Introduction to Programming (in JavaScript)

David StottsComputer Science Department

UNC Chapel Hill

Introduction to Programming

(in JavaScript)

0. data (types, simple information)

1. data storage (variables, assignment)2. data retrieval (expressions, evaluation)3. repetition (loops)4. decision making (conditionals)5. procedure abstraction (functions)6. data abstraction (arrays)

7. objects: all-the-above, wrapped up

The Big Six(6) Data Abstraction

We have been studying Arrays

We have seen “for loops” as access patterns

Contains any valid statements…◦ assignment◦ conditionals

for (i=0; i<length; i++) { sum = sum + grade[ i ] ; if (grade[i]>90) { aCount = aCount + 1; } }

Loop Body

Another complete loop?What if loop body contains…

Loops in Loops

We call them “nested ” loops

for (i=0; i<length; i++) { . . . for (k=i; k<length; k++) { . . . }

. . . }

Nested For Loops

outer loop, enclosing

inner loop, enclosed in outer

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The “Inner Loop”

and the “Outer Loop”

Inner and Outer Loops

for (i=0; i<length; i++) { . . . for (k=i; k<length; k++) { . . . } . . .

}

inner loop

outer loop

Nested For Loops

for (i=0; i<length; i++) { . . . for (k=i; k<length; k++) { . . . } . . .

}

inner loop

outer loop

Nested For Loops

1 outer iteration

many inner iterations

Formatting is CRITICAL for comprehension

for (i=0; i<length; i++) {sum = sum + grade[ i ] ;if (grade[i]>90) {aCount = aCount + 1; } else { bfCount = bfCount + 1; }total += 1;}

A Note on Indentation

Indent, block structure, be consistentfor (i=0; i<length; i++) { sum = sum + grade[ i ] ; if (grade[i]>90) { aCount = aCount + 1; } else { bfCount++; } total += 1;}

A Note on Indentation