JavaScript Refactoring

We form a wonderful community.

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

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 people
than just understood by a browser.

clarity
enables
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 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.

jslint
jshint
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 tool
probably 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/

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')) {
bulk = '<div class="progress"><div style="width: 0%;"></div></div><p>Repair
complete in <span id="timeLeft">' +
utils.formatTime(millisecondsLeft) + '</span></p>';
}
}

}
else {
Real code, one method, ~150 lines.
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

};

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.

Extract method
var progress = document.querySelector('.progress div'),
progress.style.width = Math.floor((((new Date()).getTime() -
millisecondsStart) / millisecondsTotal) * 100) + "%";

clearInterval(counter);
}
progress.style.width = Math.floor((timeFromStart / millisecondsTotal) *
100) + "%";
}, 1000);
}

this.showProgressBar(startTime,requiredTime);

Extract chunk that does one thing into a separate method.

Replace comments


this.target.entity.game.publish("decoration/
showBoost", {
});
}

this.showBoosts(entity);

Well-named method makes comment unnecessary.

Remove duplication
if (this.target.entity.is("decoration")) {
this.target.entity.game.publish("decoration/
showBoost", {
});
}

var entity = this.target.entity;
if (entity.is("decoration")) {
entity.game.publish("decoration/showBoost", {
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 {
}
var food = entity.getContractValue();
bulk = '<p>Gives you ' + food + ' food</p>';
bulk = '<p>Repair complete in ' + time + '</span></p>';
}

var bulk = entity.getInfoModeString();

Each entity class implements its own version of the method.

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')) {
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 {
}
var food = this.target.entity.getContractValue();
bulk = '<div class="progress"><div style="width: 0%;"></div></div><p>Gives you ' +
food + InfoMode.prototype.activate = function (config) {
' food in <span id="timeLeft">'+utils.formatTime(millisecondsLeft)+'</span></p>'; this.target = config.target;
var entity = this.target.entity;
bulk = '<div class="progress"><div style="width: 0%;"></div></div><p>Repair
complete in <span id="timeLeft">' + if (entity.is('castle') && wooga.castle.playerData.upgradingCastle) {
utils.formatTime(millisecondsLeft) + '</span></p>';
}
} this.deactivate();
this.manager.setMode(wooga.castle.GameModesManager.Mode.BASIC);
}
else {
return;
if(entity.is('castle')) { }

if(wooga.castle.playerData.upgradingCastle) {
if (entity.is('decoration')) {
this.deactivate(); this.target.makeDynamic();
this.manager.setMode(wooga.castle.GameModesManager.Mode.BASIC); }
return;
}
this.infoPanel.innerHTML = '<h1>' + entity.getProperName() + '</h1><div
bulk = '<p><span class="population">Supported Population: ' + class=specification>' + entity.getInfoModeString() + '</div>';
entity.definition.population
+ '</span></p>';
} else if(entity.is('decoration')) { // RADAR: [szafranek] Why is this HERE? Moving it to worldView and listening to
"entity/focused" looks better to me.
bulk = '<p>Nearby buildings get a ';
var concatBoosts = false;
this.manager.view.isFocusedEntityView = function (entityView) {
if (entity.definition.goldBoost) { return entityView === config.target;
bulk += 'gold boost of ' + entity.definition.goldBoost + '%'; };
concatBoosts = true;
}
if (entity.definition.foodBoost) { if (entity.contractState === wooga.castle.House.ContractState.STARTED) {
if(concatBoosts) { this.showProgressBar(entity.contractStartTime,
bulk += '</p><p>and a ';
}
entity.contract.requiredTime);
bulk += 'food boost of ' + entity.definition.foodBoost + '%.'; } else if (entity.contractState ===
} wooga.castle.House.ContractState.CONSTRUCTION) {
}
this.showProgressBar(entity.constructionStartTime,
} entity.contract.constructionTime);
}
this.infoPanel.innerHTML = html.replace('{bulk}', bulk);

this.manager.view.isFocusedEntityView = function (entityView) { utils.publish('view:entity/focused', {
return entityView === config.target; "entity": entity,
};
if(this.target.entity.contractState === "started") { "infoMode": this
var progress = document.querySelector('.progress div'), });
progress.style.width = Math.floor((((new Date()).getTime() - millisecondsStart) /
millisecondsTotal) * 100) + "%"; this.showBoosts(entity);

this.show();
clearInterval(counter); };
}
progress.style.width = Math.floor((timeFromStart / millisecondsTotal) * 100) + "%";
}, 1000);
}

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

//TODO move to pubsub

this.target.entity.game.publish("decoration/showBoost", {
});
}
// 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();

Original method after refactoring.
};

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

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

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chez loulou diathesis
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