The ambiguity of brackets "[]" in Javascript

The ambiguity of brackets "[]" in Javascript

This article mainly introduces the ambiguity of the brackets "[]" in Javascript. For more information, see.

Javascript Brackets have four Semantics

 

Syntax 1: declare an array

 

 

The Code is as follows:

Var ary = []; // declare an empty array

Var ary = [1, 3]; // declare an array and assign the Initial Value

 

Semantics 2: retrieve array members

The Code is as follows:

Var ary = [1, 2, 3];

Var item = ary [0];

 

Semantics 3: Define object members (you can not follow the identifier rules)

The Code is as follows:

Var obj = {};

 

// Add an attribute name for obj. name is a valid identifier, which can be defined by obj. name.

Obj ['name'] = 'jack ';

 

// Add an attribute 2a for obj. 2a is not a legal identifier (cannot begin with a number) and cannot be defined through obj.2a

Obj ['2a '] = 'test ';

 

 

Semantics 4: Get object members

The Code is as follows:

Var obj = {name: 'jack '};

Obj ['2a '] = 'test ';

 

Obj ['name']; // --> jack

Obj ['2a ']; // --> test (cannot be obtained through obj.2a)