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Javascript coding conventions (coding specifications)

亚连

May 31, 2018 am 10:31 AM

javascript js specification

这篇文章主要介绍了Javascript 编码约定(编码规范),需要的朋友可以参考下

1、使用 strict 模式

在一个作用域(包括函数作用域、全局作用域)中，可以使用

"use strict";

来开启 strict 模式。

2、缩进

用 Tab 键进行代码缩进，以节约代码大小，使用4个空格的宽度来进行缩进(JSLint 建议)。

3、符号

1) 大括号

与语句放同一行，放于最后面；仅有一行语句，也使用大括号：

if (true) {
  //true
} else {
  //false
}

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while (true) {
  //alert(1);
}

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2) 空格

在逗号、分号、冒号后加空格
在操作符前后加空格
在大括号开始符之前
在大括号结束符和 else、while 或 catch 之间
在 for 的各个部分
如：

var a = [1, 2, 3];
var obj = {
  name: &#39;name&#39;,
  value: &#39;value&#39;
};
for (var i = 0; i < 10; i++) {}
function func(a, b, c) {}

c = a + b;
if (a && b || c) {
  //if
} else {
  //else
}

try {
  //try
} catch(err) {
  //catch
}

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3) 所有语句结束后，使用 ; 号结束

4、命名

对象：使用驼峰式，如：MyClass
方法、变量：使用混合式，如：getName(), myName
常量：大写加下划线，如：MY_NAME

5、单一 var 模式

只使用一个 var 在函数顶部进行变量声明，作用如下：

1) 提供一个单一的地址已查找到函数需要的所有局部变量
2) 防止出现变量在定义前就被使用的逻辑错误
3) 帮助牢记要声明变量，尽可能少地使用全局变量
4) 更少的编码

function func() {
  var a = 1,
    b = 2, 
    sum = a + b,
    obj = {
      name: &#39;name&#39;,
      value: &#39;value&#39;
    },
  $btn = $(&#39;#btn&#39;);
  //函数体
}

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6、循环

1) for 循环

var i, arr = [];
for (i = arr.length; i--;) {
  //arr[i];
}

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注:

for (var i = 0; i < document.getElementsByName().length; i++) {
  //document.getElementsByName()[0];
}

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这种方式每次对 i 进行长度比较的使用对会进行 document 的查询，而通常 DOM 操作是非常耗时的。

2) while 循环

var arr = [], 
  i = arr.length;
while (i--) {
  //处理
}

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3) for-in 循环

var i,
  hasOwn = Object.prototype.hasOwnProperty;
for (i in man) {
  if (hasOwn.call(man, i)) { //过滤
    console.log(i, &#39;:&#39;, man[i]);
  }
}

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7、switch 选择

switch (num) {
case 0:
  //do something
  break;
case 1:
  //do something
  break;
...
default:
  //do default
}

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建议使用：

var obj = {
  &#39;0&#39;: function() {
    //do somethins
  },
  &#39;1&#39;: function() {
    // do somethis
  }, ...
}
if (obj.hasOwnProperty(num)) {
  obj[num]();
} else {
  //do default
}

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8、使用 parseInt() 的数值约定

1) 每次都具体指定进制参数：

var month = &#39;09&#39;, day = &#39;08&#39;;
month = parseInt(month, 10); //不加进制参数便会转换为八进制
day = parseInt(day, 10);

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2) 其他常用的将字符串转换为数值的方法：

+&#39;08&#39;;
Number(&#39;08&#39;);

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9、字面量模式

不建议使用构造函数来定义：

// built in constructors (avoid)
var o = new Object();
var a = new Array();
var re = new RegExp(&#39;[a-z]&#39;, &#39;g&#39;);
var s = new String();
var n = new Number();
var b = new Boolean();
throw new Error(&#39;message&#39;);

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建议使用更优的字面量模式：

// literals and primitives (prefer)
var o = {};
var a = [];
var re = /[a-z]/g;
var s = &#39;&#39;;
var n = 0;
var b = false;
throw {
  name: &#39;Error&#39;,
  message: &#39;message&#39;
}

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10、其他

1) 变量内的简写单词如果在开头则全小写：xmlDocument，如果不在开头则全大写：loadXML
2) 变量必须是有意义的英文，禁止拼音

上面是我整理给大家的，希望今后会对大家有帮助。

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