将成员添加到现有对象 [英] Adding members to an existing object

问题描述

假设我们有以下对象：

var obj = {
    fn1: function() {
    }
}

如何动态添加其他成员，比如说

how can I dynamically add another member to it, say

fn2: function() {}

推荐答案

正如其他人所指出的那样：

As others have pointed out:

obj.fn2 = function(){ ... };

请注意，如果fn2不是有效的标识符，则必须使用数组表示法对象：

Note that if "fn2" is not a valid identifier, you must instead use the 'array' notation for the object:

obj["fn2"] = function(){ ... };
obj["!! crazy-names#allowed?!"] = function(){ ... };

如果你有一个存储在变量中的属性名称，你也可以这样做：

This is also how you would do it if you had the name of the property stored in a variable:

var propName = "fn2";
obj[propName] = function(){ ... };

如果要测试对象是否存在属性，可以使用 in 运算符：

If you want to test if a property exists for an object, you can use the in operator:

if ("fn2" in obj){ ... }

如果要从对象中删除属性，请使用 delete keyword：

If you want to remove a property from an object, use the delete keyword:

var o = { a:42 };
console.log( "a" in o ); // true
delete o.a;              // Or delete o["a"]
console.log( "a" in o ); // false

要迭代对象中的所有属性，请使用 for循环中的运算符。请务必 var 该变量使其不是全局变量：

To iterate over all properties in an object, use the in operator in a for loop. Be sure to var the variable so that it isn't global:

var o = { a:42, b:17 };
var allPropertyNames  = [];
var allPropertyValues = [];
for (var propName in o){
  // If you don't do this test, propName might be a property inherited
  // by this object, and not a property on the object itself.
  if (o.hasOwnProperty(propName)){
    allPropertyNames.push(propName);
    allPropertyValues.push(o[propName]);
  }
}
console.log( allPropertyNames );  // [ "a", "z" ]
console.log( allPropertyValues ); // [ 42, 17 ]

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