This document discusses refactoring code to improve its design without changing external behavior. It notes that refactoring involves making small, incremental changes rather than large "big bang" refactorings. Code smells that may indicate a need for refactoring include duplication, long methods, complex conditional logic, speculative code, and overuse of comments. Techniques discussed include extracting methods, removing duplication, using meaningful names, removing temporary variables, and applying polymorphism. The document emphasizes that refactoring is an investment that makes future changes easier and helps avoid bugs, and encourages learning from other programming communities.

1. REFACTORING
@szafranek

2. We form a wonderful community.
Yet, we can learn a lot from other programming communities.

3. REFACTORING

4. Improving
the design of code
without changing
its external behavior

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

6. Refactoring is not...
For #1 excuse visit http://xkcd.com/303

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

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

9. enables you to
go faster
May make little sense just before a deadline.

10. makes code
clear to other
people
Not machines

11. 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

12. ;
It’s much more important to write code that will be easy to understand by other people
than just understood by a browser.

13. clarity
vs
performance

14. 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.

15. CODE SMELLS

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

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

18. 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!

19. switch/if
statements
When they’re long and complex.

20. 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.

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

22. STEP #0

23. 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

24. 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/

25. STEP #1

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

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

28. STEP #2
Refactoring catalogue

29. 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.

30. 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 {
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

31. };
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.

32. Extract method
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);
}
this.showProgressBar(startTime,requiredTime);
Extract chunk that does one thing into a separate method.

33. 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.

34. 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
});
}

35. 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.

36. Remove speculative code
switch (action) {
case "move":
break;
case "destroy":
break;
default:
break;
}

37. 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!

38. 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.

39. 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 + InfoMode.prototype.activate = function (config) {
' food in <span id="timeLeft">'+utils.formatTime(millisecondsLeft)+'</span></p>'; this.target = config.target;
} else if (entity.is('ship')) {
if(this.target.entity.contractState === "started") {
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>';
}
wooga.castle.CastleCompleteScreen.instance().show();
} this.deactivate();
this.manager.setMode(wooga.castle.GameModesManager.Mode.BASIC);
}
else {
return;
if(entity.is('castle')) { }
if(wooga.castle.playerData.upgradingCastle) {
wooga.castle.CastleCompleteScreen.instance().show();
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,
};
"entityView": entity.entityView,
if(this.target.entity.contractState === "started") { "infoMode": this
var progress = document.querySelector('.progress div'), });
timer = document.getElementById('timeLeft');
progress.style.width = Math.floor((((new Date()).getTime() - millisecondsStart) /
millisecondsTotal) * 100) + "%"; this.showBoosts(entity);
counter = setInterval(function () {
var now = new Date().getTime(), timeFromStart = now - millisecondsStart;
this.show();
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();
Original method after refactoring.
};

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

41. LEARNING MORE

42. Refactoring
Martin Fowler

43. coderetreat.org
Organize one yourself if there’s none in your city!

44. 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

45. Write code for people
Learn from others
@szafranek

46. _gee_ fingersss
chez loulou diathesis
linder6580 Pipistrula
ginza_line Ocial GDC
superfluity Łukasz Bałamut
mooong
photo credits