Loop statements are often used in program implementations, and for loops are found in most languages. There are several different USES of a for loop in javascript, and here’s how I understand them.

Type 1 :(in general, perform related operations in a loop)

var objA=document.getElementsByTagName("a");
var i,max;
for(i=0,max=objA.length;i<max;i++){
objA[i].onclick=function(){
alert(this.innerHTML);
}

}

Loop, in turn, to register the click of the hyperlink label

Type 2 :(for objects, manipulate object content)

var person={name:'wmhello',age:'28'};
var tips=''; for(var obj in person){
tips+=obj+'-->'+person[obj]+'n'

}

alert(tips)

Type 3 :(often used with arrays, performing specific operations on them)

var num=[1,3,5];
var total=0;
num.forEach(function(e){
total+=e;
});
alert(total);

This forEach loop is available in firefox and chrome