What is the difference between document.getElementBy('id') and $('#id')_Basic knowledge

The following is a brief introduction:

The first is the method of obtaining objects in js, which is relatively straightforward. If a page has multiple ids, you have to write such a long document.getElementBy("id ")

Copy code The code is as follows:

document.getElementBy( "id")

Abbreviation for document.getElementById

Personally, I recommend using the definition of document.getElementById in prototype:

Copy code The code is as follows:

function $()
{
var elements = new Array();
for (var i = 0; i < arguments.length; i )
{
var element = arguments[i];
if (typeof element == 'string')
element = document.getElementById(element);
if (arguments.length == 1)
return element;
elements.push(element);
}
return elements;
}

You can also use the following code to define:

Copy code The code is as follows:

function $(objectId) {
if(document .getElementById && document.getElementById(objectId)) {
return document.getElementById(objectId);// W3C DOM
} else if (document.all && document.all(objectId)) {
return document .all(objectId);// MSIE 4 DOM
} else if (document.layers && document.layers[objectId]) {
return document.layers[objectId];// NN 4 DOM.. note: this won't find nested layers
} else {
return false;
}
}

The second one is to get the id in jquery The method

can be found in this article

http://www.jb51.net/article/27617.htm

http://www.jb51.net/article/26702.htm