jQuery - What does this syntax mean?

I am looking at jquery.ui-1.8.11.js:

$.extend(Datepicker.prototype, {
    /* Class name added to elements to indicate already configured with a date picker. */
    markerClassName: 'hasDatepicker',

    /* Debug logging (if enabled). */
    log: function () {
        if (this.debug)
            console.log.apply('', arguments);
    },

What is开发者_如何学Go that log: function() syntax? What's it called? How can it be used?

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The second argument to an $.extend call is an Object. They're defined using curly braces {} and take key: value pairs. The value can be a function, which is what is happening for the log.

This is analogous to the following:

var myObject = {
  prop1: 'some value',
  prop2: 'some other value',
  method1: function () {
    // some code here.
  }
}

You can later call myObject.method1() to perform whatever the code inside the function is.

---

It is extending the object properties on the Datepicker.prototype object.

For example, after that statement is run, you could do:

 alert(new Datepicker().markerClassName); // alert('hasDatepicker');

 // OR

 new Datepicker().log(); // calls the function

Basically, $.extend() allows you to modify an object with additional properties (or overwrite them). Consider the following object:

 var obj = { Text: 'Hello World' };

 alert(obj.Text); // Hello World

 $.extend(obj, {
     Text: 'Something Else',
     func: function() { alert('Stuff'); }
 });

 alert(obj.Text); // Something Else
 obj.func();

---

This syntax uses JavaScript prototyping to extend a Datepicker object and add additional attributes and functions. This adds Datepicker.log as a function and Datepicker.markerClassName.

---

The second argument (begun with an opening curly brace { and ended with a closing curly brace }) to the $.extend() call is an Object literal. Generally speaking, it's shorthand for explicitly creating an object with new Object. These are roughly equivalent:

var foo = new Object;
foo.bar = 'bar';

and

var foo = {
    bar: 'bar'
};

It's also worth noting that the way functions are assigned, they are anonymous functions being assigned as values to properties of the object. As in:

var foo = new Object;
foo.method1 = function() { ... };

It is also possible to use named functions:

function fn1() { ...}
foo.method2 = fn1;

Or:

foo.method3 = function fn2() { ... };

Or:

var foo = {
    method4: function fn3() { ... }
};

There are other literals useful for shorthand in JavaScript, such as the Array literal:

var arr = ['members', 'are', 'separated', 'by', 'commas'];

And the RegExp literal (note that parsing a RegExp literal does not have the same escaping rules as passing a string to new RegExp()):

var exp = /some pattern/g; // Modifiers are after the closing slash