SinhVienIT.net Giao Trinh Javascript Hay

Trang 1/109

Gio trnh JavaScript ***CH CH NG 1 L I NI U ........................................................................................................... 4 NG 2 NH P MN JAVASCRIPT ....................................................................................... 5 2.1.Nhng JavaScript vo file HTML .................................................................................. 5 2.3. Th v ............................................................................. 7 2.3. Hi n th m t dng text ................................................................................................. 8 2.4. Giao ti p v i ng i s d ng ..................................................................................... 10 2.5. i m l i cc l nh v m r ng .................................................................................... 13 NG 3 BI N TRONG JAVASCRIPT .................................................................................. 14 3.1. Bi n v phn lo I bi n............................................................................................... 14 3.2. Bi u di n t t trong JavaScript ................................................................................ 14 3.3. Ki u d li u .............................................................................................................. 14 1.1.1. KI u nguyn (Interger) ...................................................................................... 16 1.1.2. Ki u d u ph y ng (Floating Point) ................................................................. 16 1.1.3. Ki u logic (Boolean) ......................................................................................... 16 1.1.4. Ki u chu i (String) ............................................................................................ 16 XY D NG CC BI U TH C TRONG JAVASCRIPT ................................................. 17

CH

2.

NH NGH A V PHN LO I BI U TH C ................................................................................ 17 CC TON T (OPERATOR) ................................................................................................... 17 2.1.1. Gn .................................................................................................................. 17 2.1.2. So snh ............................................................................................................ 17 2.1.3. S h c .............................................................................................................. 18 2.1.4. Chu i ............................................................................................................... 18 2.1.5. Logic ................................................................................................................ 19 2.1.6. Bitwise.............................................................................................................. 19 BI T P .................................................................................................................................... 19 2.1.7. Cu h i............................................................................................................. 19 2.1.8. Tr l i............................................................................................................... 20 3. CC L NH ................................................................................................................... 21 CU L NH I U KI N.............................................................................................................. 21 CU L NH L P ........................................................................................................................ 21 3.1.1. Vng l p for ...................................................................................................... 22 3.1.2. while................................................................................................................. 23 3.1.3. Break ............................................................................................................... 23 3.1.4. continue ........................................................................................................... 23 CC CU L NH THAO TC TRN IT NG ...................................................................... 23 3.1.5. for...in ............................................................................................................... 24 3.1.6. new .................................................................................................................. 25 3.1.7. this ................................................................................................................... 26 3.1.8. with .................................................................................................................. 26

Trang 2/109CC HM (FUNCTIONS) .......................................................................................................... 27 CC HM C S N ................................................................................................................... 27 3.1.9. eval .................................................................................................................. 28 3.1.10. parseInt ............................................................................................................ 29 3.1.11. parseFloat ........................................................................................................ 29 M NG (ARRAY) ........................................................................................................................ 30 S KI N ................................................................................................................................... 31 BI T P .................................................................................................................................... 34 3.1.12. Cu h i............................................................................................................. 34 3.1.13. Tr l i............................................................................................................... 35 4. IT IT CC IT NG TRONG JAVASCRIPT .................................................................... 37 NG NAVIGATOR ........................................................................................................ 38 NG WINDOW ............................................................................................................. 39 4.1.1. Cc thu c tnh .................................................................................................. 40 4.1.2. Cc Ph ng th c ............................................................................................. 40 4.1.3. Cc Ch ng trnh x l s ki n ........................................................................ 41 IT NG LOCATION ........................................................................................................... 41 IT NG FRAME ................................................................................................................ 41 4.1.4. Cc thu c tnh .................................................................................................. 41 4.1.5. Cc Ph ng th c ............................................................................................. 41 4.1.6. S d ng Frame ................................................................................................ 41 IT NG DOCUMENT ........................................................................................................ 45 4.1.7. Cc thu c tnh .................................................................................................. 45 4.1.8. Cc Ph ng th c ............................................................................................. 45 IT NG ANCHORS ........................................................................................................... 45 IT NG FORMS ................................................................................................................ 46 4.1.9. Cc thu c tnh .................................................................................................. 46 4.1.10. Cc Ph ng th c ............................................................................................. 46 4.1.11. Cc Ch ng trnh x l s ki n ........................................................................ 46 IT NG HISTORY ............................................................................................................. 46 4.1.12. Cc thu c tnh .................................................................................................. 46 4.1.13. Cc Ph ng th c ............................................................................................. 46 IT NG LINKS................................................................................................................... 47 4.1.14. Cc thu c tnh .................................................................................................. 47 4.1.15. Cc Ch ng trnh x l s ki n ........................................................................ 47 IT NG MATH................................................................................................................... 47 4.1.16. Cc thu c tnh .................................................................................................. 47 4.1.17. Cc Ph ng th c ............................................................................................. 47 IT NG DATE ................................................................................................................... 48 4.1.18. Cc Ph ng th c ............................................................................................. 48 IT NG STRING ............................................................................................................... 49 4.1.19. Cc Ph ng th c ............................................................................................. 49 CC PH N T C A IT NG FORM ................................................................................. 49 4.1.20. Thu c tnh type................................................................................................. 50

Trang 3/1094.1.21. 4.1.22. 4.1.23. 4.1.24. 4.1.25. 4.1.26. 4.1.27. 4.1.28. 5. Ph Ph Ph Ph Ph Ph Ph Ph nt nt nt nt nt nt nt nt IT button.................................................................................................. 50 checkbox............................................................................................. 51 File Upload.......................................................................................... 52 hidden ................................................................................................. 52 Password ............................................................................................ 53 radio ................................................................................................... 53 reset ................................................................................................... 54 select .................................................................................................. 55 NG (OBJECT MODEL) .................................................................. 56

M HNH

IT NG V THU C TNH.................................................................................................. 56 T O CC IT NG M I ..................................................................................................... 56 5.1.1. S d ng kh i t o i T ng............................................................................. 56 5.1.2. S d ng m t hm xy d ng(Constructor Function) ........................................... 56 5.1.3. L p m c l c cho cc thu c tnh c a i t ng .................................................. 56 5.1.4. nh ngh a thm cc thu c tnh cho m t ki u i t ng .................................... 56 5.1.5. nh ngh a cc cch th c ................................................................................. 56 5.1.6. S d ng cho cc tham chi u i t ng (Object References) ............................ 56 5.1.7. Xo i t ng .................................................................................................. 56 6. 7. B NG T NG K T CC T KHO .............................................................................. 56 T NG K T ................................................................................................................... 56

Trang 4/109

CH

NG 1 L I NI

U

V i HTML and Microsoft FrontPage b n bi t cch t o ra trang Web - tuy nhin ch m i m c bi u di n thng tin ch cha ph i l cc trang Web ng c kh n ng p ng cc s ki n t pha ng i dng. Hng Netscape a ra ngn ng script c tn l LiveScript th c hi n ch c n ng ny. Sau ngn ng ny c i tn thnh JavaScript t n d ng tnh i chng c a ngn ng l p trnh Java. M c d c nh ng i m t ng ng gi a Java v JavaScript, nh ng chng v n l hai ngn ng ring bi t. JavaScript l ngn ng d i d ng script c th g n v i cc file HTML. N khng c bin d ch m c trnh duy t di n d ch. Khng gi ng Java ph i chuy n thnh cc m d bin d ch, trnh duy t c JavaScript d i d ng m ngu n. Chnh v v y b n c th d dng h c JavaScript qua v d b i v b n c th th y cch s d ng JavaScript trn cc trang Web. JavaScript l ngn ng d a trn i t ng, c ngh a l bao g m nhi u ki u i t ng, v d i t ng Math v i t t c cc ch c n ng ton h c. Tuy v y JavaScript khng l ngn ng h ng i t ng nh C++ hay Java do khng h tr cc l p hay tnh th a k . JavaScript c th p ng cc s ki n nh t i hay lo i b cc form. Kh n ng ny cho php JavaScript tr thnh m t ngn ng script ng. Gi ng v i HTML v Java, JavaScript c thi t k c l p v i h i u hnh. N c th ch y trn b t k h i u hnh no c trnh duy t h tr JavaScript. Ngoi ra JavaScript gi ng Java kha c nh an ninh: JavaScript khng th c v vi t vo file c a ng i dng. Cc trnh duy t web nh Nescape Navigator 2.0 tr i c th hi n th nh ng cu l nh JavaScript c nhng vo trang HTML. Khi trnh duy t yu c u m t trang, server s g i y n i dung c a trang , bao g m c HTML v cc cu l nh JavaScript qua m ng t i client. Client s c trang t u n cu i, hi n th cc k t qu c a HTML v x l cc cu l nh JavaScript khi no chng xu t hi n. Cc cu l nh JavaScript c nhng trong m t trang HTML c th tr l i cho cc s ki n c a ng i s d ng nh kch chu t, nh p vo m t form v i u h ng trang. V d b n c th ki m tra cc gi tr thng tin m ng i s d ng a vo m khng c n n b t c m t qu trnh truy n trn m ng no. Trang HTML v i JavaScript c nhng s ki m tra cc gi tr c a vo v s thng bo v i ng i s d ng khi gi tr a vo l khng h p l . M c ch c a ph n ny l gi i thi u v ngn ng l p trnh JavaScript b n c th vi t cc script vo file HTML c a mnh.

Trang 5/109

CH

NG 2 NH P MN JAVASCRIPT

2.1.NHNG JAVASCRIPT VO FILE HTML B n c th nhng JavaScript vo m t file HTML theo m t trong cc cch sau y: y S d ng cc cu l nh v cc hm trong c p th y S d ng cc file ngu n JavaScript y S d ng m t bi u th c JavaScript lm gi tr c a m t thu c tnh HTML y S d ng th s ki n (event handlers) trong m t th HTML no Trong , s d ng c p th ... v nhng m t file ngu n JavaScript l c s d ng nhi u h n c . 2.1.1.S d ng th SCRIPTCh : Ghi ch khng c t trong c p th nh ghi ch trong file HTML. C php c a JavaScript t ng t c php c a C nn c th s d ng // hay /* ... */.

Script c a vo file HTML b ng cch s d ng c p th v . Cc th c th xu t hi n trong ph n hay c a file HTML. N u t trong ph n , n s c t i v s n sng tr c khi ph n cn l i c a v n b n c t i. Thu c tnh duy nh t c nh ngh a hi n th i cho th l LANGUAGE= dng xc nh ngn ng script c s d ng. C hai gi tr c nh ngh a l "JavaScript" v "VBScript". V i Ch ng trnh vi t b ng JavaScript b n s d ng c php sau :

// INSERT ALL JavaScript HERE

i m khc nhau gi a c php vi t cc ghi ch gi a HTML v JavaScript l cho php b n n cc m JavaScript trong cc ghi ch c a file HTML, cc trnh duy t c khng h tr cho JavaScript c th c c n nh trong v d sau y:

Dng cu i cng c a script c n c d u // trnh duy t khng di n d ch dng ny d i d ng m JavaScript. Cc v d trong Ch ng ny khng ch a c i m n c a JavaScript m c th d hi u h n. 2.1.2. S d ng m t file ngu n JavaScript

Trang 6/109 Thu c tnh SRC c a th cho php b n ch r file ngu n JavaScript cs d ng (dng Ph ng php ny hay h n nhng tr c ti p m t o n l nh JavaScript vo trang HTML). C php: ....

Thu c tnh ny r y h u d ng cho vi c chia s cc hm dng chung cho nhi u trang khc nhau. Cc cu l nh JavaScript n m trong c p th v c ch a thu c tinh SRC tr khi n c l i. V d b n mu n a dng l nh sau vo gi a c p th v :document.write("Khng tm th y file JS a vo!");

Thu c tnh SRC c th tuy t i, v d :

c

nh r b ng

a ch URL, cc lin k t ho c cc

ng d n

Ch Khi b n mu n ch ra m t xu trch d n trong m t xu khc c n s d ng d u nhy n ( ' ) phn nh xu . i u ny cho php script nh n ra xu k t .

Cc file JavaScript bn ngoi khng c ch a b t k th HTML no. Chng ch c ch a cc cu l nh JavaScript v nh ngh a hm. Tn file c a cc hm JavaScript bn ngoi c n c ui .js, v server s ph i nh x ui .js t i ki u MIME application/x-javascript. l nh ng g m server g i tr l i ph n Header c a file HTML. nh x ui ny vo ki u MIME, ta thm dng sau vo file mime.types trong ng d n c u hnh c a server, sau kh i ng

l i server: N u server khng nh x s t i file JavaScript c ch ra trong thu c tnh SRC v khng ng cch. Trong v d sau, hm bar c ch a xu "left" n m trong m t c p d u nhy kp:function bar(widthPct){ document.write(" ") }

type=application/x-javascript c ui .js t i ki u MIME application/x-javascript , Navigator

2.3. TH

V

C p th ny dng nh r n i dung thng bo cho ng i s d ng bi t trnh duy t khng h tr JavaScript. Khi trnh duy t s khng hi u th v n b l i, cn o n m n m trong c p th ny s c Navigator hi n th . Ng c l i, n u trnh duy t c h tr JavaScript th o n m trong c p th s c b qua. Tuy nhin, i u ny c ng c th x y ra n u ng i s d ng khng s d ng JavaScript trong trnh duy t c a mnh b ng cch t t n i trong h p Preferences/Advanced.

Trang 7/109 V d : Trang ny c s d ng JavaScript. Do b n c n s d ng trnh duy t Netscape Navigator t version 2.0 tr i!
Hy kch chu t vo y t i v phin b n Netscape m i h n N u b n s d ng trnh duy t Netscape t 2.0 tr i m v n c c dng ch ny th hy b t Preferences/Advanced/JavaScript ln Hnh 2.3: Minh ho th NOSCRIPT 2.3. HI N TH M T DNG TEXTTrong h u h t cc ngn ng l p trnh, m t trong nh ng kh n ng c s l hi n th ra mn hnh m t dng text. Trong JavaScript, ng i l p trnh c ng c th i u khi n vi c xu t ra mn hnh c a client m t dng text tu n t trong file HTML. JavaScript s xc nh i m m n s xu t ra trong file HTML v dng text k t qu s c d ch nh cc dng HTML khc v hi n th trn trang. H n n a, JavaScript cn cho php ng i l p trnh sinh ra m t h p thng bo ho c xc nh n g m m t ho c hai nt. Ngoi ra, dng text v cc con s cn c th hi n th trong tr ng TEXT v TEXTAREA c a m t form. Trong ph n ny, ta s h c cch th c write() v writeln() c a i t ng document.Trang 8/109 i t ng document trong JavaScript c thi t k s n hai cch th c xu t m t dng text ra mn hnh client: write() v writeln(). Cch g i m t cch th c c a m t i t ng nh sau:object_name.property_nameD li u m cch th c dng d :th c hi n cng vi c c a ndocument.write("Test"); document.writeln('Test');c a vo dng tham s , vCch th c write() xu t ra mn hnh xu Text nh ng khng xu ng dng, cn cch th c writeln() sau khi vi t xong dng Text t ng xu ng dng. Hai cch th c ny u cho php xu t ra th HTML.V d : Cch th c write() xu t ra th HTML Ouputting Text This text is plain.
Trang 9/109V d : S khc nhau c a write() v writeln(): Khi duy t sc k t qu :Trang 10/109Hnh 2.5: S khc nhau c a write() v writeln() 2.4. GIAO TI P V I NG I S D NGJavaScript h tr kh n ng cho php ng i l p trnh t o ra m t h p h i tho i. N i dung c a h p h i tho i ph thu c vo trang HTML c ch a o n script m khng lm nh hng n vi c xu t n i dung trang. Cch n gi n lm vi c l s d ng cch th c alert(). s d ng c cch th c ny, b n ph i a vo m t dng text nh khi s d ng document.write() v document.writeln() trong ph n tr c. V d : alert("Nh n vo OK ti p t c"); Khi file s ch cho n khi ng i s d ng nh n vo nt OK r i m i ti p t c th c hi n Thng th ng, cch th c alert() c s d ng trong cc tr ng h p: y Thng tin a v form khng h p l y K t qu sau khi tnh ton khng h p l y Khi d ch v cha s n sng truy nh p d li uTrang 11/109Tuy nhin cch th c alert() m i ch cho php thng bo v i ng i s d ng ch ch a th c s giao ti p v i ng i s d ng. JavaScript cung c p m t cch th c khc giao ti p v i ng i s d ng l promt(). T ng t nh alert(), prompt() t o ra m t h p h i tho i v i m t dng thng bo do b n a vo, nh ng ngoi ra n cn cung c p m t tr ng nh p d li u vo. Ng i s d ng c th nh p vo tr ng r i kch vo OK. Khi , ta c th x l d li u do ng i s d ng v a a vo. V d : H p h i tho i g m m t dng thng bo, m t tr ng nh p d li u, m t nt OK v m t nt Cancel Ch ng trnh ny s h i tn ng i dng v sau s hi n th m t thng bo ng n s d ng tn m i a vo. V d c l u vo file Hello.html JavaScript Exemple var name=window.prompt(Hello! Whats your name ?,); document.write(Hello + name + ! I hope you like JavaScript ); Trang 12/109Hnh2.1: Hi n th c a s nh p tn Khi duy t c k t qu : V d ny hi n th d u nh c nh p vo tn v i Ph ng th c window.prompt. Gi tr t cs c ghi trong bi n c tn l name. Bi n name c k t h p v i cc chu i khc v c hi n th trong c a s c a trnh duy t nh Ph ng th c document.write.Hnh 2.2: Hi n th l i cho ngi nh pTrang 13/109 By gi b n c t ng v cc ch c n ng c th ti p t c tm hi u thm v chnh ngn ng ny. 2.5. I M L I CC L NH V MR NG KI U th HTML Thu c tnh c a th SCRIPT thu c tnh c a th SCRIPT Ghi ch trong JavaScript Ghi ch trong JavaScript cch th c JavaScript Cch th c JavaScript Cch th c c a JavaScript Cch th c JavaScripttc qua JavaScript, chng ta hyR NGM T H p ch a cc l nh JavaScript Gi a ch c a file JavaScript bn ngoi. File ny ph i c ph n ui .js nh r ngn ng script c s d ng (JavaScript ho c VBScript) nh d u ghi ch m t dng trong o n script nh d u ghi ch m t kh i trong o n script Xu t ra m t xu trn c a s hi n th i m t cch tu n t theo file HTML c o n script T ng t cch th c document.write() nh ng vi t xong t xu ng dng. Hi n th m t dng thng bo trn h p h i tho iL NH/M SCRIPT SRCLANGUAGE// /*...*/ document.write() document.writeln() alert()promt()Hi n th m t dng thng bo trong h p h i tho i ng th i cung c p m t tr ng nh p d li u ng i s d ng nh p vo.Trang 14/109CHNG 3 BI N TRONG JAVASCRIPT3.1. BI N V PHN LO I BI N Tn bi n trong JavaScript ph i b t u b ng ch hay d u g ch d i. Cc ch s khng c s d ng m u tn m t bi n nh ng c th s d ng sau k t u tin. Ph m vi c a bi n c th l m t trong hai ki u sau: y Bi n ton c c: C th c truy c p t b t k u trong ng d ng. c khai bo nh sau :x = 0;y Bi n c c b : Ch bo. Bi n c c b c truy c p trong ph m vi Ch ng trnh m n khai c khai bo trong m t hm v i t kho var nh sau:var x = 0;Bi n ton c c c th s d ng t kho var, tuy nhin i u ny khng th c s c n thi t. 3.2. BI U DI N TCh Khc v i C, trong JavaScript khng c ki u h ng s CONST bi u di n m t gi tr khng i no yTTRONG JAVASCRIPT ng trnh khng thay i. Sau yT t l cc gi tr trong Ch l cc v d v t t :8 The dog ate my shoe true3.3. KI U DLI UKhc v i C++ hay Java, JavaScript l ngn ng c tnh nh ki u th p. i u ny c ngh a l khng ph i ch ra ki u d li u khi khai bo bi n. Ki u d li u ct ng chuy n thnh ki u ph h p khi c n thi t. V d file Variable.Html: Datatype Example var fruit='apples'; var numfruit=12; numfruit = numfruit + 20; var temp ="There are " + numfruit + " " + "."; document.write(temp); Cc trnh duy t h tr JavaScript s x l chnh xc v d trn v y: a ra k t qu d iTrang 15/109Hnh 3.1: K t qu c a x l d li u Trnh di n d ch JavaScript s xem bi n numfruit c ki u nguyn khi c ng v i 20 v c ki u chu i khi k t h p v i bi n temp. Trong JavaScript, c b n ki u d li u sau y: ki u s nguyn, ki u d u ph y ng, ki u logic v ki u chu i. 1.1.1. KI U NGUYN (INTERGER) S nguyn c th c bi u di n theo ba cch: y H c s 10 (h th p phn) - c th bi u di n s nguyn theo c s 10, ch r ng ch s u tin ph i khc 0. y H c s 8 (h bt phn) - s nguyn c th bi u di n d i d ng bt phn v i ch s u tin l s 0. y H c s 16 (h th p l c phn) - s nguyn c th bi u di n d i d ng th p l c phn v i hai ch s u tin l 0x. 1.1.2. KI U D U PH Y NG (FLOATING POINT)M t literal c ki u d u ph y ng c 4 thnh ph n sau: y Ph n nguyn th p phn. y D u ch m th p phn (.). y Ph n d . y Ph n m .Trang 16/109 phn bi t ki u d u ph y d u ch m hay E. V d :9.87 -0.85E4 9.87E14 .98E-3ng v i ki u s nguyn, ph i c t nh t m t ch s theo sau1.1.3. KI U LOGIC (BOOLEAN) Ki u logic c s d ng ch c hai gi tr y true. y false. ch hai i u ki n : ng ho c sai. Mi n gi tr c a ki u ny1.1.4. KI U CHU I (STRING) M t literal ki u chu i ... " hay '... '. V d :The dog ran up the tree The dog barked 100c bi u di n b i khng hay nhi u k tct trong c p d u "bi u di n d u nhy kp ( " ), trong chu i s d ng ( \" ), v d :document.write( \This text inside quotes.\ );Trang 17/1092. XY D NG JAVASCRIPTCCBI UTH CTRONGNH NGH A V PHN LO I BI U TH CT p h p cc literal, bi n v cc ton t nh m nh gi m t gi tr no c g i l m t bi u th c (expression). V c b n c ba ki u bi u th c trong JavaScript: y S h c: Nh m l ng gi gi tr s . V d (3+4)+(84.5/3) c nh gi b ng 197.1666666667. y Chu i: Nh m nh gi chu i. V d "The dog barked" + barktone + "!" l The dog barked ferociously!. y Logic: Nh m nh gi gi tr logic. V d temp>32 c th nh n gi tr sai. JavaScript c ng h tr bi u th c i u ki n, c php nh sau:(condition) ? valTrue : valFalseN u i u ki n condition c nh gi l ng, bi u th c nh n gi tr valTrue, ng c l i nh n gi tr valFalse. V d :state = (temp>32) ? "liquid" : "solid"Trong v d ny bi n state c gn gi tr "liquid" n u gi tr c a bi n temp l n h n 32; trong tr ng h p ng c l i n nh n gi tr "solid".CC TON T(OPERATOR)Ton t c s d ng th c hi n m t php ton no trn d li u. M t ton t c th tr l i m t gi tr ki u s , ki u chu i hay ki u logic. Cc ton t trong JavaScript c th c nhm thnh cc lo i sau y: gn, so snh, s h c, chu i, logic v logic bitwise. 2.1.1. GN Ton t gn l d u b ng (=) nh m th c hi n vi c gn gi tr c a ton h ng bn ph i cho ton h ng bn tri. Bn c nh JavaScript cn h tr m t s ki u ton t gn rt g n. Ki u gn thng th ng x=x+y x=x-y x=x*y x=x/y x=x%y 2.1.2. SO SNH Ng i ta s d ng ton t so snh so snh hai ton h ng v tr l i gi tr ng hay sai ph thu c vo k t qu so snh. Sau y l m t s ton t so snh trong JavaScript: Ki u gn rt g n x+=y x-=y x*=y x/=y x%=yTrang 18/109== != > >= < 2 tr thnh 4 (s nh phn 10000 tr thnh s nh phn 100) >>> Ton t d ch ph i c chn 0. D ch chuy n ton h ng tri sang ph i m t s l ng bit b ng ton h ng ph i. Bit d u c d ch chuy n t tri (gi ng >>). Nh ng bit c d ch sang ph i b xo i. V d : -8>>>2 tr thnh 1073741822 (b i cc bit d u tr thnh m t ph n c a s ). T t nhin v i s d ng k t qu c a ton t >> v >>> l gi ng nhau.C m t s ton t d ch chuy n bitwise rt g n: Ki u bitwise thng th ng x = x > y x = x >>> y x=x&y x=x^y x=x|y Ki u bitwise rt g n x > y x >>> = y x&=y x^=y x|=yTrang 20/109BI T P2.1.7. CU H I Hy nh gi cc bi u th c sau: 1. a. 7 + 5 b. "7" + "5" c. 7 == 7 d. 7 >= 5 e. 7 = 5) && (5 > 5) h. (7 >= 5) || (5 > 5) 2.1.8. TR Cc bi u th c 1. a. 12 b. "75" c. true d. true e. true 2. f. 5 g. false h. true L I c nh gi nh sau:Trang 21/1093.CC L NHnh c a JavaScript thnh ba nhm sau: nh i u ki n. nh l p. nh tho tc trn i t ng.C th chia cc l L L LCU L NHI U KI NyCu l nh i u ki n cho php Ch ng trnh ra quy t nh v th c hi n cng vi c no d a trn k t qu c a quy t nh. Trong JavaScript, cu l nh i u ki n l if...elseif ... elseCu l nh ny cho php b n ki m tra i u ki n v th c hi n m t nhm l nh no y d a trn k t qu c a i u ki n v a ki m tra. Nhm l nh sau else khng b t bu c ph i c, n cho php ch ra nhm l nh ph i th c hi n n u i u ki n l sai. C phpif ( < i u ki n> ) { //Cc cu l nh v i i u ki n ng } else { //Cc cu l nh v i i u ki n sai }V d :if (x==10){ document.write(x b ng 10, x = 0; } else document.write(x khng b ng 10.); t l i x b ng 0.);Ch K t { v }c s d ngtch cc kh i m.CU L NH L PCu l nh l p th hi n vi c l p i l p l i m t o n m cho n khi bi u th c i u ki n c nh gi l ng. JavaScipt cung c p hai ki u cu l nh l p:Trang 22/109 y y for loop while loop3.1.1. VNG L P FOR Vng l p for thi t l p m t bi u th c kh i u - initExpr, sau l p m t o n m cho n khi bi u th c < i u ki n> c nh gi l ng. Sau khi k t thc m i vng l p, bi u th c incrExpr c nh gi l i. C php: for (initExpr; < i u ki n> ; incrExpr){ //Cc l nh c th c hi n trong khi l p } V d : For loop Example for (x=1; x10.Vng l p while l p kh i l nh ch ng no < i u ki n> cn C php: while (< i u ki n>) { //Cc cu l nh th c hi n trong khi l p } V d :x=1; while (x