js imitates html5 placeholder to adapt to unsupported browsers_javascript skills

HTML5 natively supports placeholder. For browsers that do not support it (ie), js simulation can be used.
js code

Copy code The code is as follows:

( function(){
//Determine whether placeholder is supported
function isPlaceholer(){
var input = document.createElement('input');
return "placeholder" in input;
}
//Unsupported code
if(!isPlaceholer()){
//Create a class
function Placeholder(obj){
this.input = obj;
this .label = document.createElement('label');
this.label.innerHTML = obj.getAttribute('placeholder');
this.label.style.cssText = 'position:absolute; text-indent: 4px;color:#999999; font-size:12px;';
if(obj.value != ''){
this.label.style.display = 'none';
}
this.init();
}
Placeholder.prototype = {
//Get the position
getxy: function(obj){
var left, top;
if(document .documentElement.getBoundingClientRect){
var html = document.documentElement,
body = document.body,
pos = obj.getBoundingClientRect(),
st = html.scrollTop || body.scrollTop,
sl = html.scrollLeft || body.scrollLeft,
ct = html.clientTop || body.clientTop,
cl = html.clientLeft || body.clientLeft;
left = pos.left sl - cl;
top = pos.top st - ct;
}
else{
while(obj){
left = obj.offsetLeft;
top = obj.offsetTop ;
obj = obj.offsetParent;
}
}
return{
left: left,
top : top
}
},
// Get width and height
getwh : function(obj){
return {
w : obj.offsetWidth,
h : obj.offsetHeight
}
},
//Add Width and height value method
setStyles: function(obj,styles){
for(var p in styles){
obj.style[p] = styles[p] 'px';
}
},
init : function(){
var label = this.label,
input = this.input,
xy = this.getxy(input),
wh = this .getwh(input);
this.setStyles(label, {'width':wh.w, 'height':wh.h, 'lineHeight':20, 'left':xy.left, 'top': xy.top});
document.body.appendChild(label);
label.onclick = function(){
this.style.display = "none";
input.focus() ;
}
input.onfocus = function(){
label.style.display = "none";
};
input.onblur = function(){
if( this.value == ""){
label.style.display = "block";
}
};
}
}
var inpColl = document.getElementsByTagName(' input'),
textColl = document.getElementsByTagName('textarea');
//HTML collection is converted into an array
function toArray(coll){
for(var i = 0, a = [ ], len = coll.length; i < len; i ){
a[i] = coll[i];
}
return a;
}
var inpArr = toArray (inpColl),
textArr = toArray(textColl),
placeholderArr = inpArr.concat(textArr);
for (var i = 0; i < placeholderArr.length; i ){
if (placeholderArr[i].getAttribute('placeholder')){
new Placeholder(placeholderArr[i]);
}
}
}
})()

html code:

Copy code The code is as follows:

< ;br>

css code:

Copy code The code is as follows:

div,input,textarea{ margin:0 ; padding:0;}
div{width:400px; margin:100px auto 0;}
input,textarea{width:200px;height:20px; margin-top:5px;line-height:20px;border :1px #666666 solid; background-color:#fff; padding-left:2px;}
textarea{ height:60px; font-size:12px; resize:none;}