This link: https: //blog.csdn.net/qq_36209248/article/details/89190978
By default, there is no return of the function return value is undefined (i.e., does not define a return value), if the return is defined, the specified object is returned.
But the constructors compare t special, new default constructor returns the newly created object in the case of no return. In the case of return of the case, it is divided into two cases to consider:
If the return value is the basic data type (string, number, boolean, undefined , null), then the new object instance return value, i.e. this.
A function S = var () {
in this.x =. 3;
return. 1;
}
var B = new new A ();
the console.log (A); // {X:. 3}
If the return value is a non-basic data types the object, the function returns a value of the specified object, the object referenced by this value is discarded.
A function S = var () {
in this.x =. 3;
return A;
}
var B = new new A ();
the console.log (B);} A //S(){this.x=3;return
intuitive example:
var a = function User( name, age){
this.name = name;
this.age = age;
// return; // return the this
// return null; // return the this
// return the this; // return the this
// return to true; // return the this
// return 'String'; // return the this
// return. 1 ; // return the this
// returns above {name: "ha", Age: 18 is}
// return []; // return new []
// return function () {}; // return the new function, discard the this
// return new new Boolean (to false); // returns the new boolean, discard the this
// return new new String ( 'Hello World'); // returns the new string, discard the this
// Number the new new return (32); // returns the new number, abandon the this
}
var b = new new a ( "ha ha", 18)
console.log (b);
mainly JS - new and return the contents of their own to do a bit of finishing, for their future review.
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Original link: https: //blog.csdn.net/qq_36209248/article/details/89190978