The $ dollar symbol is also used in JavaScript to replace document. getelementbyid.

CopyCodeThe Code is as follows: function $ (ID) {return document. getelementbyid (ID );

The previous version of the browser is no problem, if you use an old browser, you can use the following functionCopy codeThe Code is as follows: function $ (objectid ){
If (document. getelementbyid & document. getelementbyid (objectid )){
// W3C dom
Return document. getelementbyid (objectid );
}
Else if (document. All & document. All (objectid )){
// MSIE 4 dom
Return document. All (objectid );
}
Else if (document. Layers & document. Layers [objectid]) {
// NN 4 Dom.. Note: This won't find nested Layers
Return document. Layers [objectid];
}
Else {
Return false;
}
}

To implement $ instead of document. the effect of getelementbyid is simple, but it does not reference prototype, jquery, and other frameworks. getelementbyid, which can be used everywhere after being defined in a public Javascript file.