$ in jQuery
1.The jQuery wrapper:Select and wrap DOM elements to operate upon
The $() function (an alias for the jQuery() function) returns a special Java-Script object containing an array of the DOM elements that match the selector. Such as:
$("body > div"); //This selector selects direct <div> children of <body>.
2.Utility functions:begins with "$.",Serve as a namespace for global utility functions
$.trim(someString); //Identical to jQuery.trim(someString);
3.The document ready handler
When the page DOM has fully loaded (but only the DOM, exclude the images and others resources), the function inside the "$()" will execute!
$(function() {
$("table tr:nth-child(even)").addClass("even");
});
//not like window.onload=function(){...} ,window.onload will execute when the page has completely loaded!!
4.Making DOM elements:
$("<p>Hi there!</p>") // create a new paragraph element
5.Extending jQuery
$("form#myForm input.special").disable();