Encapsulate your own class class so that the browser recognizes the method of obtaining the element by className
Principle: (Core)
We need to take out all the boxes and use the traversal method to judge by the className of each box . Leave if equal.
< script > window . onload = function (){ // Encapsulate your own class name function getClass ( classname ){ // If the browser supports it, return directly if ( document . getElementsByClassName ) { return document . getElementsByClassName ( classname ); } // Unsupported browsers var arr = []; // Array used to store satisfied var dom =
document.getElementsByTagName("*");//alert(dom.length);for(var i=0;i<dom.length;i++) {if(dom[i].className == classname) {arr.push(dom[i]); } }return arr; }
console.log(getClass("demo").length); }</script>
end, split version