JavaScript Refactoring

REFACTORING

@szafranek

We form a wonderful community.

Yet, we can learn a lot from other programming communities.

REFACTORING

Improving the design of code without changing its external behavior

Refactoring is not...

If the changes affect external behavior, it’s rewriting, not refactoring.

Refactoring is not...

For #1 excuse visit http://xkcd.com/303

continuous

small steps

Refactoring should be done as a part of our every day workflow.Don’t wait for massive “big bang” refactorings.

Investment

When to refactor?It’s an investment:- Makes change easier.- Helps find bugs.But comes with time and effort cost.

enables you to go faster

May make little sense just before a deadline.

makes code clear to other

people

Not machines

Martin Fowler“Any fool can write code that a computer can understand.Good programmers write code that humans can understand.”

From the book “Refactoring”:http://www.amazon.com/Refactoring-Improving-Design-Existing-Code/dp/0201485672

;It’s much more important to write code that will be easy to understand by other peoplethan just understood by a browser.

clarityvs

performance

clarityenables

performance

Some of you have heard that “Premature optimization is the root of all evil”.

It's easier to optimize clean code than to clean up "optimized" code.

CODE SMELLS

Code is like cheese.Some people find smelly what other find deliciously wonderful.

duplication

It makes change harder.The rule of 3: the third time you copy something, it’s time to refactor.

long methods

More than 10 lines is long. This rule is arbitrary to force you to stop and think when you exceed this size.A method should do one thing!

switch/if statements

When they’re long and complex.

speculative code

Remove any code that “may be useful later”. You can always recover it from version control.

Very often such code is NEVER nedeed and just confuses people who encounter it.

comments

Comments become bad when used as a deodorant to hide messy code.

STEP #0

jslintjshint

Static analysis tools that detect mistakes and enforce clear style.Using lint was the single most important boost to my productivity in writing JS

John Carmack“Anything that isn’t crystal clear to a static analysis toolprobably isn’t clear to your fellow programmers”.From John Carmack’s great article on static analysis tools:http://altdevblogaday.com/2011/12/24/static-code-analysis/

STEP #1

UNIT TESTS

Tests give a safety net. How else do you know that you didn’t change the behavior?

JavaScript developer’s typical reaction to a question about unit tests

STEP #2

Refactoring catalogue

What you learned about webstandards and clean front-end code is still valid. These are the basics:* Separation of concerns.* Use CSS for styling.* Don’t inline JavaScript.* Assemble HTML in templates.

InfoMode.prototype.activate = function (config) {

this.target = config.target; var entity = this.target.entity, entityName = entity.getProperName(), bulk = entity.getInfoModeString(), html = '<h1>' + entityName + '</h1><div class=specification>{bulk}</div>', millisecondsStart, millisecondsTotal, millisecondsEnd, millisecondsLeft;

if(entity.is('decoration')) { this.target.makeDynamic(); }

this.infoPanel.innerHTML = "";

if(entity.contract) { millisecondsStart = entity.contractStartTime; millisecondsTotal = entity.contract.requiredTime; millisecondsEnd = (new Date()).getTime() - this.target.entity.contractStartTime; millisecondsLeft = millisecondsTotal-millisecondsEnd;

if (entity.is('any house')) { if(this.target.entity.contractState === "started") { var gold = this.target.entity.getContractValue(); bulk = '<div class="progress"><div style="width: 0%;"></div></div><p>Gives you '+ gold + ' coins in <span id="timeLeft">'+utils.formatTime(millisecondsLeft)+'</span></p>'; } else { bulk = bulk || '<p>Please connect to road</p>'; } } else if (entity.is('farm')) { var food = this.target.entity.getContractValue(); bulk = '<div class="progress"><div style="width: 0%;"></div></div><p>Gives you ' + food + ' food in <span id="timeLeft">'+utils.formatTime(millisecondsLeft)+'</span></p>'; } else if (entity.is('ship')) { if(this.target.entity.contractState === "started") { bulk = '<div class="progress"><div style="width: 0%;"></div></div><p>Repair complete in <span id="timeLeft">' + utils.formatTime(millisecondsLeft) + '</span></p>'; } }

} else { if(entity.is('castle')) {

if(wooga.castle.playerData.upgradingCastle) { wooga.castle.CastleCompleteScreen.instance().show(); this.deactivate(); this.manager.setMode(wooga.castle.GameModesManager.Mode.BASIC); return; }

bulk = '<p><span class="population">Supported Population: ' + entity.definition.population + '</span></p>'; } else if(entity.is('decoration')) {

bulk = '<p>Nearby buildings get a '; var concatBoosts = false; if (entity.definition.goldBoost) { bulk += 'gold boost of ' + entity.definition.goldBoost + '%'; concatBoosts = true; } if (entity.definition.foodBoost) { if(concatBoosts) { bulk += '</p><p>and a '; } bulk += 'food boost of ' + entity.definition.foodBoost + '%.'; }

} }

this.infoPanel.innerHTML = html.replace('{bulk}', bulk);

this.manager.view.isFocusedEntityView = function (entityView) { return entityView === config.target; };

if(this.target.entity.contractState === "started") { var progress = document.querySelector('.progress div'), timer = document.getElementById('timeLeft'); progress.style.width = Math.floor((((new Date()).getTime() - millisecondsStart) / millisecondsTotal) * 100) + "%";

counter = setInterval(function () { var now = new Date().getTime(), timeFromStart = now - millisecondsStart; if((timeFromStart / millisecondsTotal) >= 1) { clearInterval(counter); } timer.innerHTML = utils.formatTime(millisecondsTotal - timeFromStart); progress.style.width = Math.floor((timeFromStart / millisecondsTotal) * 100) + "%"; }, 1000); }

utils.publish('view:entity/focused', { "entity": entity, "entityView": entity.entityView, "infoMode": this });

//TODO move to pubsub

// show boost info in influence area of decoration if (this.target instanceof wooga.castle.DecorationView) { this.target.entity.game.publish("decoration/showBoost", { entityView: this.target, x: this.target.entity.x, y: this.target.entity.y }); } // show boost of houses or farmfields in info mode if (this.target instanceof wooga.castle.FarmFieldView || this.target instanceof wooga.castle.HouseView) { if (this.target.entity.boost) { this.target.entity.entityView.showBoostInfo = true; } }

this.show();

};

Real code, one method, ~150 lines.











} }








this.show();

};

Real code, one method, ~150 lines.

Extract method



this.showProgressBar(startTime,requiredTime);

Extract chunk that does one thing into a separate method.

Replace comments

// show boost info in influence area of decoration

if (this.target instanceof wooga.castle.DecorationView) { this.target.entity.game.publish("decoration/showBoost", { entityView: this.target, x: this.target.entity.x, y: this.target.entity.y }); }

this.showBoosts(entity);

Well-named method makes comment unnecessary.

Remove duplication

if (this.target.entity.is("decoration")) { this.target.entity.game.publish("decoration/showBoost", { entityView: this.target, x: this.target.entity.x, y: this.target.entity.y });}

var entity = this.target.entity;if (entity.is("decoration")) { entity.game.publish("decoration/showBoost", { entityView: this.target, x: entity.x, y: entity.y });}

Replace temp with a query

var text = entity.getInfoModeString();infoPanel.innerHTML = '<div>' + text + '</div>';

infoPanel.innerHTML ='<div>' + entity.getInfoModeString() + '</div>';

If temporary variable is used only once, it doesn’t make sense to introduce it.Sometimes even two calls don’t justify a temporary variable, unless they’re expensive and you want to cache the results.

Remove speculative code

switch (action) { case "move": break; case "destroy": break; default: break;}

Use meaningful names

var p = this.current.params;var r = this.current.results;if (r.restProduct) { p.query = r.restProduct;}

var params = this.current.params;var results = this.current.results;if (results.restProduct) { params.query = results.restProduct;}

There are 2 hard things in CS: “cache invalidation and naming things”.

Leave compression to minifiers!

Use polymorphism

if (entity.is('house')) { if(entity.contractState === "started") { var gold = entity.getContractValue(); bulk = '<p>Gives you '+ gold + ' coins</p>'; } else { bulk = bulk || '<p>Please connect to road</p>'; }} else if (entity.is('farm')) { var food = entity.getContractValue(); bulk = '<p>Gives you ' + food + ' food</p>';} else if (entity.is('ship')) { bulk = '<p>Repair complete in ' + time + '</span></p>';}

var bulk = entity.getInfoModeString();

Each entity class implements its own version of the method.











} }








this.show();

};

InfoMode.prototype.activate = function (config) { this.target = config.target; var entity = this.target.entity;

if (entity.is('castle') && wooga.castle.playerData.upgradingCastle) { wooga.castle.CastleCompleteScreen.instance().show(); this.deactivate(); this.manager.setMode(wooga.castle.GameModesManager.Mode.BASIC); return; }

if (entity.is('decoration')) { this.target.makeDynamic(); }

this.infoPanel.innerHTML = '<h1>' + entity.getProperName() + '</h1><div class=specification>' + entity.getInfoModeString() + '</div>';

// RADAR: [szafranek] Why is this HERE? Moving it to worldView and listening to "entity/focused" looks better to me. this.manager.view.isFocusedEntityView = function (entityView) { return entityView === config.target; };

if (entity.contractState === wooga.castle.House.ContractState.STARTED) { this.showProgressBar(entity.contractStartTime, entity.contract.requiredTime); } else if (entity.contractState === wooga.castle.House.ContractState.CONSTRUCTION) { this.showProgressBar(entity.constructionStartTime, entity.contract.constructionTime); }


this.showBoosts(entity);

this.show();

};

Original method after refactoring.

Know where to stop.Ask yourself: is the further investment wortwhile?

LEARNING MORE

RefactoringMartin Fowler

http://www.amazon.com/Refactoring-Improving-Design-Existing-Code/dp/0201485672

http://www.amazon.com/Refactoring-Improving-Design-Existing-Code/dp/0201485672

coderetreat.org

Organize one yourself if there’s none in your city!

Robert C. Martin“Learning to write clean code is hard work.It requires more than just the knowledge of principles and patterns.You must sweat over it. You must practice it yourself, and watch yourself fail.You must watch others practice it and fail.”

From the book “Clean Code”:http://www.amazon.com/Clean-Code-Handbook-Software-Craftsmanship/dp/0132350882

Write code for people

Learn from others

@szafranek

photo credits

Ocial GDCginza_line

superfluity

_gee_

Pipistrula

fingersss

Łukasz Bałamut

mooong

diathesis

linder6580

chez loulou

http://www.flickr.com/photos/officialgdc/

http://www.flickr.com/photos/officialgdc/

http://www.flickr.com/photos/ginza-line/

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http://www.flickr.com/photos/equanimity/

http://www.flickr.com/photos/equanimity/

http://www.flickr.com/photos/pipistrula/

http://www.flickr.com/photos/pipistrula/

http://www.flickr.com/photos/60906583@N08/

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http://www.flickr.com/photos/moofbong/

http://www.flickr.com/photos/moofbong/

http://www.flickr.com/photos/diathesis/

http://www.flickr.com/photos/diathesis/

http://www.sxc.hu/profile/linder6580

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http://www.flickr.com/photos/chez_loulou/

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JavaScript Refactoring

Technology

static analysis

gold

entityname

food

timefromstart

target instanceof

millisecondstotal

population