JavaScript编码风格

最新推荐文章于 2020-07-15 09:20:14 发布

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最新推荐文章于 2020-07-15 09:20:14 发布

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本文提供了一套详细的JavaScript编码规范，包括使用JSHint进行错误检测、代码缩进、空格使用、赋值语句格式、严格等号使用、类型检查、注释规范、引用符号选择及DOM节点操作的最佳实践。

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一些达成共识的JavaScript编码风格约定

http://www.youkuaiyun.com/article/2013-07-11/2816196-javascript-code-style-guide

JavaScript Style Guide

1. Linting

Use JSHint to detect errors and potential problems. Every jQuery project has a Grunt task for linting all JavaScript files:grunt jshint. The options for JSHint are stored in a .jshintrc file; many repositories will have multiple .jshintrc files based on the type of code in each directory.

Each .jshintrc file follows a specific format. All options must be alphabetized and grouped:

{
    "common1": true,
    "common2": true,
 
    "repoSpecific1": true,
    "repoSpecific2": true,
 
    "globals": {
        "repoGlobal1": true,
        "repoGlobal2": false
    }
}

The following common options must be used in all projects:

{
    "boss": true,
    "curly": true,
    "eqeqeq": true,
    "eqnull": true,
    "expr": true,
    "immed": true,
    "noarg": true,
    "onevar": true,
    "quotmark": "double",
    "smarttabs": true,
    "trailing": true,
    "undef": true,
    "unused": true
}

2. Spacing

Indentation with tabs.
No end of line whitespace.
No blank line whitespace.
Liberal spacing in code.
if/else/for/while/try always have braces and always go on multiple lines.

Bad Examples

// Bad
if(condition) doSomething();
 
// Bad
while(condition) iterating++;
 
// Bad
for(var i=0;i<100;i++) someIterativeFn();
 
// Bad
object[array[0]];

Good Examples

// Good
if ( condition ) {
    // expressions
}
 
// Good
while ( condition ) {
    // expressions
}
 
// Good
var i = 0;
 
for ( ; i < 100; i++ ) {
    // expressions
}
 
// Good
var prop;
 
for ( prop in object ) {
    // expressions
}
 
// Good
if ( condition ) {
    // expressions
} else {
    // expressions
}
 
// Good
if ( condition ) {
    // expressions
} else if ( condition ) {
    // expressions
} else {
    // expressions
}
 
// Good
try {
    // expressions
} catch ( e ) {
    // expressions
}
 
// Good
try {
    // expressions
} catch ( e ) {
    // expressions
} finally {
    // expressions
}
 
// Good
object[ array[ 0 ] ];

Arrays and Objects

Empty objects and arrays don't need filler spaces

var object = {},
    array = [];

Function Calls

Always include extra spaces around the arguments:

foo( arg );
 
foo( "string", object );
 
foo( options, callback );
 
foo( node, "property", 2 );

Exceptions:

// Empty function calls
foo();
 
// Functions with callbacks
foo(function() {
    // Note there is no extra space between the first paren
    // of the executing function call and the word "function"
});
 
// Function accepting an array, no space
foo([ "alpha", "beta" ]);
 
 
// Function accepting an object, no space
foo({
    a: "alpha",
    b: "beta"
});

3. Assignments

Assignments should always have a semicolon after them.

Semicolons should always be followed by a newline.

Assignments in a declaration should always be on their own line. Declarations that don't have an assignment should be listed together at the start of the declaration. For example:

// Bad
var foo = true;
var bar = false;
var a;
var b;
var c;
 
// Good
var a, b, c,
    foo = true,
    bar = false;

4. Equality

Strict equality checks (===) should be used in favor of ==. The only exception is when checking for undefined and null by way of null.

// Check for both undefined and null values, for some important reason.
undefOrNull == null;

5. Type Checks

String: typeof object === "string"
Number: typeof object === "number"
Boolean: typeof object === "boolean"
Object: typeof object === "object"
Plain Object: jQuery.isPlainObject( object )
Function: jQuery.isFunction( object )
Array: jQuery.isArray( object )
Element: object.nodeType
null: object === null
null or undefined: object == null
undefined:
- Global Variables: typeof variable === "undefined"
- Local Variables: variable === undefined
- Properties: object.prop === undefined

6. Comments

Single line comments go OVER the line they refer to:

// We need an explicit "bar", because later in the code foo is checked.
var foo = "bar";

For long comments, use:

/*
Four score and seven—pause—minutes ago...
*/

Inline comments are allowed as an exception when used to annotate special arguments in formal parameter lists:

function foo( types, selector, data, fn, /*INTERNAL*/ one ) {
    // do stuff.
}

7. Quotes

jQuery uses double quotes.

var double = "I am wrapped in double quotes";

Strings that require inner quoting must use double outside and single inside.

var html = "<div id='my-id'></div>";

8. DOM Node Rules

.nodeName should always be used in favor of .tagName.

.nodeType should be used to determine the classification of a node (not .nodeName).