Use of the JavaScript object class method

1. Get the property name

var o = {p1:123, p2:456}; Object.keys (o);//Get an enumerable property name//["P1", "P2"] Object.getownpropertynames (o); Get all property names//["P1", "P2"]

2. Get the information description of the attribute

var o = {p: ' a '};           Object.getownpropertydescriptor (o, ' P ')//Object {value: "A", Writable:true, Enumerable:true, Configurable:true}

3. Define a property

Object.defineproperty (Object, PropertyName, Attributesobject)

The first parameter is the target object, the second argument is the property name, and the third is the property description

Var o = object.defineproperty ({},  "P", {                              value: 123,                              writable :  false, //can write                              enumerable: true,                               configurable: false });                       o.p // 123                      o.p = 246;                      o.p // 123 //  because writable is false, So the value of this property cannot be changed

Define multiple properties

Var o = object.defineproperties ({}, {                                                  p1: { value: 123, enumerable: true },                                                        p2: { value:  "ABC ", enumerable: true },                                                        p3: {                                                        //get: function ()  { return this.p1+this.p2 },                                                        VALUE: THIS.P1+THIS.P2,                                                                Whether        enumerable:true,//can be enumerated                                                                     configurable:true //Property Description can be modified                                                           }                                           });  o.p1 // 123 o.p2 //   "abc"  o.p3 //  "123abc"

Note that get cannot be present at the same time as value or writable to describe unified properties

4. Check whether the property is enumerable

Object.prototype.propertyIsEnumerable () user.propertyisenumerable (' toString ');

5. Prohibit dynamic expansion of objects

Object.preventextensions (object);

var o = new Object (); Object.isextensible (o)//True Object.preventextensions (O); Object.isextensible (o)

6. Freeze the object so that it becomes a constant object (cannot extend properties and methods)

var o = {p: "Hello"}; Object.freeze (o); O.P = "World"; O.P//Hello o.t = "Hello"; O.T//undefined

Use of the JavaScript object class method