用js为单form表单添加input id和label for

window.onload= function(){

var WrapDiv = document.getElentById('bg-main');

var  theLabel = document.getElementsByTagName('label');

var  theInput = document.getElementsByTagName('input');

for(i = 0; i<theInput.length;  i++){

theInput[i].id = 'c' + i;

}

for(j = 0; j<theLabel.length; j++){

theLabel[j].setAttribute('for','c'+j);

}

}