单击使用string.prototype

Question

I'm trying to create an extension method named .Switch() like this:

    String.prototype.Switch = function (p) {
        console.log(this); // should log $obj
    };

    var $obj = $("div");
    $("a", $obj).click(function (e) {
        $obj.Switch(0);
    });

HTML

 <div>
   <a href="#">Link</a>
 </div>

And I'm getting an error: Uncaught TypeError: undefined is not a function

Can someone show me how this is done?

Answer 1

$obj is a jQuery object, not a string. If you want to add functions to it, you should do so in this way:

jQuery.fn.Switch = function (p) {
     console.log(this); // should log $obj
};

Answer 2

The error your getting is because you are extending the String Object by adding a Switch function to the prototype. However, the function your calling Switch on is a JQuery Object. So If we Modify your example:

String.prototype.Switch = function (p) {
    console.log(p); // should log input
};

var testStr = 'hello'; // create a new instance of String Object

testStr.Switch(5); // will log 5

So similarly if you declare the function on the prototype of the JQuery object you will be able to call that function from all instances of the JQuery Object.

Answer 3

var $obj = $("div"); is a jQuery object. You could do var $obj = $("div").text(); which would call Switch with a string instead of an object.

You need to do $.prototype.Switch to log the object.