HTML5 attribute placeholder JS backwards compatible support (jquery version)

Source: Internet
Author: User

Placeholder is the HTML5 form characteristics of the more useful one, but suffer from its backward compatibility, so generally to do backward-compatible sites are not afraid to use, if useful to the place, is also a simple simulation with JS to achieve, then there is no one to solve the problem once and for all?

And then I'm going to take you to this program:

if inch return;

This code means to determine whether the placeholder property is supported, and if so, return without executing the code below.

if (This is thisreturn;

Of course, if the type of input is a button, there is no need to placeholder.

Next, we start to implement the

function (opts) {    = $.extend ({},opts);     return this. each (function() {        //main code    });  }

The code above is the basic code to write the extension $.fn plug-in, the following method will be placed in the jquery selector return value, that is, the $ (selector) inside the direct call.

Since $ () returns may be an array of jquery objects, the plug-in will typically be each,return as standard notation, allowing jquery to link up, such as $ (). function ().

The basic frame is set up, open and dry!

var_this = $ ( This);varPlaceholdertext = _this.attr (' placeholder ') | | ‘‘;if( This. Type = = ' Text ' | | This. Type = = ' Email ') {     This. Value =Placeholdertext; _this.on (' Focus ',function() {        if( This. Value = = Placeholdertext) This. Value = ' ';    }); _this.on (' Blur ',function() {        if( This. Value = = ") This. Value =Placeholdertext; });}

This is each input in each, first get the value of placeholder, and cache it up.

Judging type is ' text ' | | ' Email ' time to execute the following (HTML5 input type more, here first do the two support, here do not do email authentication);
The above code is a way to solve the common container, and then the most difficult type= ' password '.

varID = This. ID;if(id = = = ") {     This. id = ' Placeholderbuild_ ' +Base.supportid; ID= ' Placeholderbuild_ ' +Base.supportid;}varLabel = $ (' <label for= "' + ID + '" > ' + placeholdertext + ' </label> '));varCSS = {    ' Left ': 5-$ ( This). Outerwidth (true),    ' Width ': $ ( This). Outerwidth (true),    ' Height ': $ ( This). Outerheight (true),    ' Line-height ': $ ( This). Outerheight (true) + ' px ',    ' Position ': ' absolute ', opacity:' 0.5 '};varValim = $ (' <span></span> ')). css ({position:' Relative '}); Label.css (CSS). AppendTo (Valim); Valim.insertafter ($ ( This));$( This). On (' Focus ',function() {label.hide ();}). On (' Blur ',function() {    if( This. Value = = ") Label.show ();});

The assignment id,base is a global variable object.

The general idea is to create an empty <span> behind input, then append a label in the empty span and set the label's for ID to the ID of input (for the HTML5 attribute, so here is a slight contradiction).

The label is assigned a wide height, position, left,top,opacity and so on.

Then continue to bind the Focus,blur method.

It's so simple.

Called when, directly in the

$ (function () {
$ (' input '). Placeholdersupport ();
});

When there is an asynchronous DOM input that needs support, only the group will find this input, and then:
$ (input). Placeholdersupport ();

Code write is very old, not how to optimize, base can be replaced with $, you can also use their own global variable object.
Complete source code is attached:

Placeholdersupport:function() {            if(' Placeholder 'inchDocument.createelement (' input '))return  This; if(!base.supportid) {Base.supportid= 0; }            return  This. each (function(e) {Base.supportid++; if( This. Type = = ' Submit ' | | This. Type = = ' button ' | | This. Type = = ' reset ')return; varPlaceholdertext = $ ( This). attr (' placeholder ') | | ‘‘; if( This. Type = = ' Text ' | | This. Type = = ' Email ') {                     This. Value =Placeholdertext; $( This). On (' Focus ',function() {                        if( This. Value = = Placeholdertext) This. Value = ' ';                    }); $( This). On (' Blur ',function() {                        if( This. Value = = ") This. Value =Placeholdertext;                }); } Else if(Placeholdertext!== ' && This. Type = = = ' Password ') {                    varID = This. ID; if(id = = = ") {                         This. id = ' Placeholderbuild_ ' +Base.supportid; ID= ' Placeholderbuild_ ' +Base.supportid; }                    varLabel = $ (' <label for= "' + ID + '" > ' + placeholdertext + ' </label> ')); varCSS = {                        ' Left ': 5-$ ( This). Outerwidth (true),                        ' Width ': $ ( This). Outerwidth (true),                        ' Height ': $ ( This). Outerheight (true),                        ' Line-height ': $ ( This). Outerheight (true) + ' px ',                        ' Position ': ' absolute ', opacity:' 0.5 '                    }; varValim = $ (' <span></span> ')). css ({position:' Relative '                    });                    Label.css (CSS). AppendTo (Valim); Valim.insertafter ($ ( This)); $( This). On (' Focus ',function() {label.hide (); }). On (' Blur ',function() {                        if( This. Value = = ") label.show ();                });        }            }); }

HTML5 attribute placeholder JS backwards compatible support (jquery version)

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