How can I check the existence of an element in jQuery?
The current code that I have is this:
if ($(selector).length > 0) {
// Do something
}
Is there a more elegant way to approach this? Perhaps a plugin or a function?
In JavaScript, everything is 'truthy' or 'falsy', and for numbers 0 (and NaN) means false, everything else true. So you could write:
if ($(selector).length)
You don't need that >0 part.
NaN != false. - Robert[] + [] = ""... ahh I love javascript - James
Yes!
jQuery.fn.exists = function(){ return this.length > 0; }
if ($(selector).exists()) {
// Do something
}
This is in response to: Herding Code podcast with Jeff Atwood
$.fn.exists example is replacing a property lookup (cheap!) with two function calls, which are much more expensive—and one of those function calls recreates a jQuery object that you already have, which is just silly. - C Snover.exists reads cleanly, whereas .length reads as something semantically different, even if the semantics coincide with an identical result. - Ben Zotto
If you used
jQuery.fn.exists = function(){return ($(this).length > 0);}
if ($(selector).exists()) { }
you would imply that chaining was possible when it is not.
This would be better:
jQuery.exists = function(selector) {return ($(selector).length > 0);}
if ($.exists(selector)) { }
Alternatively, from the FAQ:
if ( $('#myDiv').length ) { /* Do something */ }
You could also use the following. If there are no values in the jQuery object array then getting the first item in the array would return undefined.
if ( $('#myDiv')[0] ) { /* Do something */ }
$(".missing").css("color", "red") already does the right thing… (i.e. nothing) - Ben Blank$.fn methods that return something other than a new jQuery object and therefore don't chain. - Alnitak
You can use this:
// if element exists
if($('selector').length){ /* do something */ }
// if element does not exist
if(!$('selector').length){ /* do something */ }
The fastest and most semantically self explaining way to check for existence is actually by using plain JavaScript:
if (document.getElementById('element_id')) {
// Do something
}
It is a bit longer to write than the jQuery length alternative, but executes faster since it is a native JS method.
And it is better than the alternative of writing your own jQuery function. That alternative is slower, for the reasons @snover stated. But it would also give other programmers the impression that the exists() function is something inherent to jQuery. JavaScript would/should be understood by others editing your code, without increased knowledge debt.
NB: Notice the lack of an '#' before the element_id (since this is plain JS, not jQuery).
$('#foo a.special'). And it can return more than one element. getElementById can't begin to approach that. - kikitoif(document.querySelector("#foo a.special")) would work. No jQuery needed. - Blue Skies
You can save a few bytes by writing:
if ($(selector)[0]) { ... }
This works because each jQuery object also masquerades as an array, so we can use the array dereferencing operator to get the first item from the array. It returns undefined if there is no item at the specified index.
jQuery.first() or jQuery.eq(0) both return objects, objects are truthy even if they are empty-ish. This example should illustrate why these functions cannot be used as-is: if(jQuery("#does-not-exist").eq(0)) alert("#does-not-exist exists") - Salman A.eq(0) returns just another jQuery object truncated to length 1 or 0. .first() is just a convenience method for .eq(0). But .get(0) returns the first DOM element or undefined and is the same as [0]. The first DOM element in a jQuery object is stored in the regular object property with the name '0'. That's a simple property access. The only type casting stems from the implicit conversion of the number 0 to the string '0'. So if type casting is a problem you could use $.find(selector)['0'] instead. - Robert
You can use:
if ($(selector).is('*')) {
// Do something
}
A little more elegant, perhaps.
666 probably have plenty of other reasons their code's broken. While it is an invalid selector, $(666).length is valid javascript: It evaluates to truthy, and therefore should satisfy the condition. - Todd$.find(666).length works. - Emile Bergeron
This plugin can be used in an if statement like if ($(ele).exist()) { /* DO WORK */ } or using a callback.
;;(function($) {
if (!$.exist) {
$.extend({
exist: function() {
var ele, cbmExist, cbmNotExist;
if (arguments.length) {
for (x in arguments) {
switch (typeof arguments[x]) {
case 'function':
if (typeof cbmExist == "undefined") cbmExist = arguments[x];
else cbmNotExist = arguments[x];
break;
case 'object':
if (arguments[x] instanceof jQuery) ele = arguments[x];
else {
var obj = arguments[x];
for (y in obj) {
if (typeof obj[y] == 'function') {
if (typeof cbmExist == "undefined") cbmExist = obj[y];
else cbmNotExist = obj[y];
}
if (typeof obj[y] == 'object' && obj[y] instanceof jQuery) ele = obj[y];
if (typeof obj[y] == 'string') ele = $(obj[y]);
}
}
break;
case 'string':
ele = $(arguments[x]);
break;
}
}
}
if (typeof cbmExist == 'function') {
var exist = ele.length > 0 ? true : false;
if (exist) {
return ele.each(function(i) { cbmExist.apply(this, [exist, ele, i]); });
}
else if (typeof cbmNotExist == 'function') {
cbmNotExist.apply(ele, [exist, ele]);
return ele;
}
else {
if (ele.length <= 1) return ele.length > 0 ? true : false;
else return ele.length;
}
}
else {
if (ele.length <= 1) return ele.length > 0 ? true : false;
else return ele.length;
}
return false;
}
});
$.fn.extend({
exist: function() {
var args = [$(this)];
if (arguments.length) for (x in arguments) args.push(arguments[x]);
return $.exist.apply($, args);
}
});
}
})(jQuery);
You may specify one or two callbacks. The first one will fire if the element exists, the second one will fire if the element does not exist. However, if you choose to pass only one function, it will only fire when the element exists. Thus, the chain will die if the selected element does not exist. Of course, if it does exist, the first function will fire and the chain will continue.
Keep in mind that using the callback variant helps maintain chainability – the element is returned and you can continue chaining commands as with any other jQuery method!
if ($.exist('#eleID')) { /* DO WORK */ } // param as STRING
if ($.exist($('#eleID'))) { /* DO WORK */ } // param as jQuery OBJECT
if ($('#eleID').exist()) { /* DO WORK */ } // enduced on jQuery OBJECT
$.exist('#eleID', function() { // param is STRING && CALLBACK METHOD
/* DO WORK */
/* This will ONLY fire if the element EXIST */
}, function() { // param is STRING && CALLBACK METHOD
/* DO WORK */
/* This will ONLY fire if the element DOES NOT EXIST */
})
$('#eleID').exist(function() { // enduced on jQuery OBJECT with CALLBACK METHOD
/* DO WORK */
/* This will ONLY fire if the element EXIST */
})
$.exist({ // param is OBJECT containing 2 key|value pairs: element = STRING, callback = METHOD
element: '#eleID',
callback: function() {
/* DO WORK */
/* This will ONLY fire if the element EXIST */
}
})
Has Items callback actually pass in the object as an argument? - Chris Marisic
There's no need for jQuery really. With plain JavaScript it's easier and semantically correct to check for:
if(document.getElementById("myElement")) {
//Do something...
}
If for any reason you don't want to put an id to the element, you can still use any other JavaScript method designed to access the DOM.
jQuery is really cool, but don't let pure JavaScript fall into oblivion...
I see most of the answers here are not accurate as they should be, they check element length, it can be OK in many cases, but not 100%, imagine if number pass to the function instead, so I prototype a function which check all conditions and return the answer as it should be:
$.fn.exists = $.fn.exists || function() {
return !!(this.length && (this[0] instanceof HTMLDocument || this[0] instanceof HTMLElement));
}
This will check both length and type, Now you can check it this way:
$(1980).exists(); //return false
$([1,2,3]).exists(); //return false
$({name: 'stackoverflow', url: 'http://www.stackoverflow.com'}).exists(); //return false
$([{nodeName: 'foo'}]).exists() // returns false
$('div').exists(); //return true
$('.header').exists(); //return true
$(document).exists(); //return true
$('body').exists(); //return true
You could use this:
jQuery.fn.extend({
exists: function() { return this.length }
});
if($(selector).exists()){/*do something*/}
The reason all of the previous answers require the .length parameter is that they are mostly using jquery's $() selector which has querySelectorAll behind the curtains (or they are using it directly). This method is rather slow because it needs to parse the entire DOM tree looking for all matches to that selector and populating an array with them.
The ['length'] parameter is not needed or useful and the code will be a lot faster if you directly use document.querySelector(selector) instead, because it returns the first element it matches or null if not found.
function elementIfExists(selector){ //named this way on purpose, see below
return document.querySelector(selector);
}
/* usage: */
var myelement = elementIfExists("#myid") || myfallbackelement;
However this method leaves us with the actual object being returned; which is fine if it isn't going to be saved as variable and used repeatedly (thus keeping the reference around if we forget).
var myel=elementIfExists("#myid");
// now we are using a reference to the element which will linger after removal
myel.getParentNode.removeChild(myel);
console.log(elementIfExists("#myid")); /* null */
console.log(myel); /* giant table lingering around detached from document */
myel=null; /* now it can be garbage collected */
In some cases this may be desired. It can be used in a for loop like this:
/* locally scoped myel gets garbage collected even with the break; */
for (var myel; myel = elementIfExist(sel); myel.getParentNode.removeChild(myel))
if (myel == myblacklistedel) break;
If you don't actually need the element and want to get/store just a true/false, just double not it !! It works for shoes that come untied, so why knot here?
function elementExists(selector){
return !!document.querySelector(selector);
}
/* usage: */
var hastables = elementExists("table"); /* will be true or false */
if (hastables){
/* insert css style sheet for our pretty tables */
}
setTimeOut(function (){if (hastables && !elementExists("#mytablecss"))
alert("bad table layouts");},3000);
I have found if ($(selector).length) {} to be insufficient. It will silently break your app when selector is an empty object {}.
var $target = $({});
console.log($target, $target.length);
// Console output:
// -------------------------------------
// [▼ Object ] 1
// ► __proto__: Object
My only suggestion is to perform an additional check for {}.
if ($.isEmptyObject(selector) || !$(selector).length) {
throw new Error('Unable to work with the given selector.');
}
I'm still looking for a better solution though as this one is a bit heavy.
Edit: WARNING! This doesn't work in IE when selector is a string.
$.isEmptyObject('hello') // FALSE in Chrome and TRUE in IE
$() with an empty object as an argument? - nnnnnn{} to $()? - cpburnz
You can check element is present or not using length in java script. If length is greater than zero then element is present if length is zero then element is not present
// These by Id
if( $('#elementid').length > 0){
// Element is Present
}else{
// Element is not Present
}
// These by Class
if( $('.elementClass').length > 0){
// Element is Present
}else{
// Element is not Present
}
Is $.contains() what you want?
jQuery.contains( container, contained )The
$.contains()method returns true if the DOM element provided by the second argument is a descendant of the DOM element provided by the first argument, whether it is a direct child or nested more deeply. Otherwise, it returns false. Only element nodes are supported; if the second argument is a text or comment node,$.contains()will return false.Note: The first argument must be a DOM element, not a jQuery object or plain JavaScript object.
$(selector).length && //Do something
if where an if would improve readability at the cost of 2 bytes. - Emile Bergeron&& for you. - user7892745
Checking for existence of an element is documented neatly in the official jQuery website itself!
Use the .length property of the jQuery collection returned by your selector:
if ($("#myDiv").length) { $("#myDiv").show(); }Note that it isn't always necessary to test whether an element exists. The following code will show the element if it exists, and do nothing (with no errors) if it does not:
$("#myDiv").show();
this is very similar to all of the answers, but why not use the ! operator twice so you can get a boolean:
jQuery.fn.exists = function(){return !!this.length};
if ($(selector).exists()) {
// the element exists, now what?...
}
Boolean(x) can sometimes be more efficient. - user7892745
Try testing for DOM element
if (!!$(selector)[0]) // do stuff
Inspired by hiway's answer I came up with the following:
$.fn.exists = function() {
return $.contains( document.documentElement, this[0] );
}
jQuery.contains takes two DOM elements and checks whether the first one contains the second one.
Using document.documentElement as the first argument fulfills the semantics of the exists method when we want to apply it solely to check the existence of an element in the current document.
Below, I've put together a snippet that compares jQuery.exists() against the $(sel)[0] and $(sel).length approaches which both return truthy values for $(4) while $(4).exists() returns false. In the context of checking for existence of an element in the DOM this seems to be the desired result.
$.fn.exists = function() {
return $.contains(document.documentElement, this[0]);
}
var testFuncs = [
function(jq) { return !!jq[0]; },
function(jq) { return !!jq.length; },
function(jq) { return jq.exists(); },
];
var inputs = [
["$()",$()],
["$(4)",$(4)],
["$('#idoexist')",$('#idoexist')],
["$('#idontexist')",$('#idontexist')]
];
for( var i = 0, l = inputs.length, tr, input; i < l; i++ ) {
input = inputs[i][1];
tr = "<tr><td>" + inputs[i][0] + "</td><td>"
+ testFuncs[0](input) + "</td><td>"
+ testFuncs[1](input) + "</td><td>"
+ testFuncs[2](input) + "</td></tr>";
$("table").append(tr);
}td { border: 1px solid black }<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="idoexist">#idoexist</div>
<table style>
<tr>
<td>Input</td><td>!!$(sel)[0]</td><td>!!$(sel).length</td><td>$(sel).exists()</td>
</tr>
</table>
<script>
$.fn.exists = function() {
return $.contains(document.documentElement, this[0]);
}
</script>
I just like to use plain vanilla javascript to do this.
function isExists(selector){
return document.querySelectorAll(selector).length>0;
}
I had a case where I wanted to see if an object exists inside of another so I added something to the first answer to check for a selector inside the selector..
// Checks if an object exists.
// Usage:
//
// $(selector).exists()
//
// Or:
//
// $(selector).exists(anotherSelector);
jQuery.fn.exists = function(selector) {
return selector ? this.find(selector).length : this.length;
};
I stumbled upon this question and i'd like to share a snippet of code i currently use:
$.fn.exists = function(callback) {
var self = this;
var wrapper = (function(){
function notExists () {}
notExists.prototype.otherwise = function(fallback){
if (!self.length) {
fallback.call();
}
};
return new notExists;
})();
if(self.length) {
callback.call();
}
return wrapper;
}
And now i can write code like this -
$("#elem").exists(function(){
alert ("it exists");
}).otherwise(function(){
alert ("it doesn't exist");
});
It might seem a lot of code, but when written in CoffeeScript it is quite small:
$.fn.exists = (callback) ->
exists = @length
callback.call() if exists
new class
otherwise: (fallback) ->
fallback.call() if not exists
No need for jQuery
if(document.querySelector('.a-class')) {
// do something
}
How about:
function exists(selector) {
return $(selector).length;
}
if (exists(selector)) {
// do something
}
It's very minimal and saves you having to enclose the selector with $() every time.
if($("#thing").exists(){} reads as. Also, it's not the jQuery way. - 1j01
I'm using this:
$.fn.ifExists = function(fn) {
if (this.length) {
$(fn(this));
}
};
$("#element").ifExists(
function($this){
$this.addClass('someClass').animate({marginTop:20},function(){alert('ok')});
}
);
Execute the chain only if a jQuery element exist - http://jsfiddle.net/andres_314/vbNM3/2/
Here is my favorite exist method in jQuery
$.fn.exist = function(callback) {
return $(this).each(function () {
var target = $(this);
if (this.length > 0 && typeof callback === 'function') {
callback.call(target);
}
});
};
and other version which supports callback when selector does not exist
$.fn.exist = function(onExist, onNotExist) {
return $(this).each(function() {
var target = $(this);
if (this.length > 0) {
if (typeof onExist === 'function') {
onExist.call(target);
}
} else {
if (typeof onNotExist === 'function') {
onNotExist.call(target);
}
}
});
};
Example:
$('#foo .bar').exist(
function () {
// Stuff when '#foo .bar' exists
},
function () {
// Stuff when '#foo .bar' does not exist
}
);
$("selector") give an object which has length data. If there are elements as you define in selector, you will get them from the object. So if you check it's length you allready can find, is there any element exists. In javascript 0 == false also null == false . If you not get 0 your codes will run.
if($("selector").length){
//code in the case
}
if ( $('#myDiv').size() > 0 ) { //do something }
size() counts the number of elements returned by the selector
.size() does nothing more than return .length. There's a reason it's deprecated - Ian.length, being a property, requires slightly less overhead than a function call to .size(). My bad. - Furbeenator
You don't have to check if it's greater than 0 like $(selector).length > 0, $(selector).length it's enough and a elegant way to check the existence of elements. I don't think that is worth to write a function only for this, if you want to do more extra things, yes.
if($(selector).length){
// true if length is not 0
} else {
// false if length is 0
}