Implement a function extend

NOW, today, let us extend to implement a function.

Specific ideas: the use Object.defineProperty () characteristics attribute set, and () acquired by the attribute descriptor Object.getOwnPropertyDescriptor, and assigned to the newly created object

Let's pull the code out yo

    Object.defineProperty (Object.prototype,
         "Extend" , 
        { 
            Writable: to true , 
            Enumerable: to false , 
            Configurable: to true , 
            value: function (O) {
                 // Get all properties owned 
                var names = Object.getOwnPropertyNames (O);
                 for ( var I = 0; I <of names.length; I ++ ) {
                     // if the attribute exists skip 
                    IF (names [I] in  the this ) Continue ;
                    // get attributes of the attribute descriptor SS 
                    var desc = Object.getOwnPropertyDescriptor (O, names [I]); 
                    Object.defineProperty ( the this , names [I], desc) 
                } 
            } 
        }             
    )   

Example of use:

  // define a new object 
    var A = { 
        itemA: . 1 
    } 
    // create a new attribute, and set the attribute descriptor 
    Object.defineProperty (A, "itemB" , { 
        Writable: to true , 
        Enumerable: to false , 
        Configurable: to true , 
        value: 2 
    }) 
    // then define a new object 
    var B = {} 
    b.extend (a) 
    // At this point we can see the static properties have inherited passed 
    the console.log (B)   // results {itemA: 1, itemB: 2} 
    // look at the property descriptor is not also passed
    let extendDesc = Object.getOwnPropertyDescriptor(b,"itemB")
    console.log(extendDesc)  // 结果为{value: 2, writable: true, enumerable: false, configurable: true}

Well, the end, we have the opportunity to work together to achieve what analog Object.create () function