推荐编码规范

下面是 Cocos Creator 开发团队使用的编码规范，收录在手册里以供游戏开发者和工具开发者参考。

命名规范

• 当我们为变量，函数和实例命名时, 使用 camelCase 命名法。

  // bad
  var FOOBar = {};
  var foo_bar = {};
  function FOOBar () {}
  
  // good
  var fooBar = {};
  function fooBar () {}

• 当我们为类或者模块命名时，使用 PascalCase 命名法。

  // bad
  var foobar = cc.Class({
      foo: 'foo',
      bar: 'bar',
  });
  var foobar = require('foo-bar');
  
  // good
  var FooBar = cc.Class({
      foo: 'foo',
      bar: 'bar',
  });
  var FooBar = require('foo-bar');

• 推荐使用全大写加下划线来命名“常量”。

  // bad
  const PRIVATE_VARIABLE = 'should not be unnecessarily uppercased within a file';
  
  // bad
  var THING_TO_BE_CHANGED = 'should obviously not be uppercased';
  
  // bad
  let REASSIGNABLE_VARIABLE = 'do not use let with uppercase variables';
  
  // ---
  
  // allowed but does not supply semantic value
  export const apiKey = 'SOMEKEY';
  
  // better in most cases
  export const API_KEY = 'SOMEKEY';
  
  // ---
  
  // bad - unnecessarily uppercases key while adding no semantic value
  export const MAPPING = {
      KEY: 'value'
  };
  
  // good
  export const Type = {
      SIMPLE: 'value'
  };

• 使用前置下划线 _ 当我们为私有属性命名

  // bad
  this.__firstName__ = 'foobar';
  this.firstName_ = 'foobar';
  
  // good
  this._firstName = 'foobar';

• 文件名我们采用 dash 命名法

  // bad
  fooBar.js
  FooBar.js
  
  // good
  foo-bar.js

语法规范

• 使用 Object.create(null) 创建一个字典

  // bad
  var map = new Object();
  
  // bad
  var map = {};
  
  // good
  var map = Object.create(null);

• 使用 [] 创建一个数组

  // bad
  var array = new Array();
  
  // good
  var array = [];

• 尽可能在 js 代码中使用单引号 '' 来定义 string

  // bad
  var str = "Hello World";
  
  // good
  var str = 'Hello World';

• 多行 string 定义时, 尽可能使用 + 定义

  // bad
  const errorMessage = 'This is a super long error that was thrown because of Batman. When you stop to think about how Batman had anything to do with this, you would get nowhere fast.';
  
  // bad
  const errorMessage = 'This is a super long error that was thrown because \
  of Batman. When you stop to think about how Batman had anything to do \
  with this, you would get nowhere \
  fast.';
  
  // good
  const errorMessage = 'This is a super long error that was thrown because ' +
    'of Batman. When you stop to think about how Batman had anything to do ' +
    'with this, you would get nowhere fast.';

• 使用 === 和 !== 而不是 == 和 !=

书写规范

• 根据个人习惯, 和原代码作者格式, 选择 4 个空格或者 2 个空格作为缩进

  // bad
  function () {
  ∙var name;
  }
  
  // very bad
  function () {
  ∙∙<tab>∙∙var name;
  }
  
  // good
  function () {
  ∙∙var name;
  }
  
  // good
  function () {
  ∙∙∙∙var name;
  }

• 行尾不要留有空格，文件底部请留一个空行

  // bad
  function () {∙
  ∙∙∙∙var name;∙
  }
  /* EOF */
  
  // good
  function () {
  ∙∙∙∙var name;
  }
  
  /* EOF */

• 语句结尾请加 ;

  // bad
  proto.foo = function () {
  }
  
  // good
  proto.foo = function () {
  };
  
  // bad
  function foo () {
      return 'test'
  }
  
  // very bad
  //   returns `undefined` instead of the value on the next line,
  //   always happens when `return` is on a line by itself because of Automatic Semicolon Insertion!
  function foo () {
      return
          'test'
  }
  
  // good
  function foo () {
      return 'test';
  }
  
  // bad
  function foo () {
  };
  
  // good，这里不是语句结尾
  function foo () {
  }

• 尽可能将 { 和表达式放在同一行

  // bad
  if ( isFoobar )
  {
  }
  
  // good
  if ( isFoobar ) {
  }
  
  // bad
  function foobar ()
  {
  }
  
  // good
  function foobar () {
  }
  
  // bad
  var obj =
  {
      foo: 'foo',
      bar: 'bar',
  }
  
  // good
  var obj = {
      foo: 'foo',
      bar: 'bar',
  }

• 在 { 前请空一格

  // bad
  if (isJedi){
      fight();
  }
  else{
      escape();
  }
  
  // good
  if (isJedi) {
      fight();
  }
  else {
      escape();
  }
  
  // bad
  dog.set('attr',{
      age: '1 year',
      breed: 'Bernese Mountain Dog',
  });
  
  // good
  dog.set('attr', {
      age: '1 year',
      breed: 'Bernese Mountain Dog',
  });

• 在逻辑状态表达式 ( if, else, while, switch) 后请空一格

  // bad
  if(isJedi) {
      fight ();
  }
  else{
      escape();
  }
  
  // good
  if (isJedi) {
      fight();
  }
  else {
      escape();
  }

• 二元、三元运算符的左右请空一格

  // bad
  var x=y+5;
  var left = rotated? y: x;
  
  // good
  var x = y + 5;
  var left = rotated ? y : x;
  
  // bad
  for (let i=0; i< 10; i++) {
  }
  
  // good
  for (let i = 0; i < 10; i++) {
  }

• 一些函数的声明方式

  // bad
  var test = function () {
      console.log('test');
  };
  
  // good
  function test () {
      console.log('test');
  }
  
  // bad
  function test () { console.log('test'); };
  
  // good
  function test () {
      console.log('test');
  }
  
  // bad
  function divisibleFunction () {
      return DEBUG ? 'foo' : 'bar';
  }
  
  // best
  var divisibleFunction = DEBUG ?
      function () {
          return 'foo';
      } :
      function () {
          return 'bar';
      };
  
  // bad
  function test(){
  }
  
  // good
  function test () {
  }
  
  // bad
  var obj = {
      foo: function () {
      }
  };
  
  // good
  var obj = {
      foo () {
      }
  };
  
  // bad
  array.map(x=>x + 1);
  array.map(x => {
      return x + 1;
  });
  
  // good
  array.map(x => x + 1);

• 在 Block 定义之间请空一行

  // bad
  if (foo) {
      return bar;
  }
  return baz;
  
  // good
  if (foo) {
      return bar;
  }
  
  return baz;
  
  // bad
  const obj = {
      x: 0,
      y: 0,
      foo () {
      },
      bar () {
      },
  };
  return obj;
  
  // good
  const obj = {
      x: 0,
      y: 0,
  
      foo () {
      },
  
      bar () {
      },
  };
  
  return obj;

• 不要使用前置逗号定义

  // bad
  var story = [
        once
      , upon
      , aTime
  ];
  
  // good
  var story = [
      once,
      upon,
      aTime,
  ];
  
  // bad
  var hero = {
        firstName: 'Ada'
      , lastName: 'Lovelace'
      , birthYear: 1815
      , superPower: 'computers'
  };
  
  // good
  var hero = {
      firstName: 'Ada',
      lastName: 'Lovelace',
      birthYear: 1815,
      superPower: 'computers',
  };

• 单行注释请在斜杠后面加一个空格

  //bad
  // good

• 多行注释写法

  /*
   * good
   */

• 需要导出到 API 文档的多行注释写法

  /**
   * good
   */

• 除了多语言 API 注释以外，代码中不允许写中文注释

  // bad
  // 中文注释不利于非中文开发者阅读代码
  // good
  // Please write all in file comments in English

推荐阅读

Airbnb JavaScript Style Guide