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Is there an "exists" function for jQuery?

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?


M
MartinNajemi

In JavaScript, everything is 'truthy' or 'falsy', and for numbers 0 means false, everything else true. So you could write:

if ($(selector).length)

You don't need that >0 part.


@abhirathore2006 If you use an id selector and the element doesn't exist then length is 0 and doesn't throw exceptions.
Interestingly enough NaN != false.
@James That's because [].toString() === [].join(',') === "" and "" === "".
@Robert, that's because NaN != a when a is literally any value.
NaN may be != false, but NaN is definitely falsy, which is a slightly different thing
J
Jake McGraw

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


I just write: if( $(selector).length ){ ... } without the '> 0'
The $.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.
@redsquare: Code readability is the best rationale for adding this sort of function on jQuery. Having something called .exists reads cleanly, whereas .length reads as something semantically different, even if the semantics coincide with an identical result.
@quixoto, sorry but .length is a standard across many languages that does not need wrapping. How else do you interpret .length?
In my opinion, it's at least one logical indirection from the concept of "a list length that is greater than zero" to the concept of "the element(s) I wrote a selector for exist". Yeah, they're the same thing technically, but the conceptual abstraction is at a different level. This causes some people to prefer a more explicit indicator, even at some performance cost.
R
R3tep

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 */ }

There are already methods that aren't chainable, like attr and data functions. I do see your point though and, for what it's worth, I just test for length > 0 anyways.
Why on earth would you need to chain this? $(".missing").css("color", "red") already does the right thing… (i.e. nothing)
D
Derek 朕會功夫

You can use this:

// if element exists
if($('selector').length){ /* do something */ }

// if element does not exist
if(!$('selector').length){ /* do something */ }

Did you not see that Tim Büthe had already given this answer 2 years prior to you?
Pfft, Tim never showed how to test if the element does not exist.
R
Randika Vishman

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).


Totally not the same thing. JQuery selectors can be used for any CSS rule - for example $('#foo a.special'). And it can return more than one element. getElementById can't begin to approach that.
@Noz if(document.querySelector("#foo a.special")) would work. No jQuery needed.
The argument of speed in JS engines is only dead in the mind of people who can't function without jQuery, since it's an argument they can't win.
Remember the good old days when document.getElementById was all we had? And I always forgot the document. and couldn't figure out why it didn't work. And I always spelled it wrong and got the character casing wrong.
S
Salman A

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.


No, 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")
D
Devon

You can use:

if ($(selector).is('*')) {
  // Do something
}

A little more elegant, perhaps.


This is too much for such a simple thing. see Tim Büthe answer
This is the correct answer. The 'length' method has the problem that it gives false positive with any number, for example: $(666).length // returns 1, but it's not a valid selector
This is extremely expensive for very simple task. Just look into jquery implementation if .is() and you will see how much code it needs to process to answer you this simple question. Also it is not obvious what you want to do exactly, so it is same or maybe less elegant then solution in question.
2
22 revs, 6 users 64%

This plugin can be used in an if statement like if ($(ele).exist()) { /* DO WORK */ } or using a callback.

Plugin

;;(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);

jsFiddle

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!

Example Uses

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    */
    }
})

On the callback version, shouldn't the Has Items callback actually pass in the object as an argument?
A
Alireza

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

P
Peter Mortensen

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 know: it doesn't answer directly the original question (which asks for a jquery function), but in that case the answer would be "No" or "not a semantically correct solution".
B
Bellash

You could use this:

jQuery.fn.extend({
    exists: function() { return this.length }
});

if($(selector).exists()){/*do something*/}

t
technosaurus

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);

C
Community

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.


This doesn't accept a selector, which means he would have to select it, which means he could just check the result of his selection.
R
ROOT

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
}

You need not to check weather length is greater than 0, if( $('#elementid').length ) { } will be sufficient.
Have you actually read the question? It's exactly the same method OP is using.
O
Oleg

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

How often do you find yourself calling $() with an empty object as an argument?
@nnnnnn Actually never (I don't use jQuery anymore). But I guess 3 years ago I had a case of exposing an API that would take a selector and return the number of elements for that selector. If another dev would pass in an empty object, it would incorrectly respond with 1.
Why on earth would you pass an empty object {} to $()?
@cpburnz why do you ask me? I was just an API provider... People pass all kinds of stupid things to APIs.
Just noticed, the jquery issue thread that @FagnerBrack referenced was updated shortly after his comment; it looks like it's not going away after all.
P
Palec

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();


S
Santiago Hernández

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?...
}

Because Boolean(x) can sometimes be more efficient.
S
SJG
$(selector).length && //Do something

I hate these clever ways of avoiding to use an if where an if would improve readability at the cost of 2 bytes.
Plus, minifiers will do all these && for you.
Haha now 8 years later it is so common in React JS 😄
g
guest271314

Try testing for DOM element

if (!!$(selector)[0]) // do stuff

t
tagurit

No need for jQuery (basic solution)

if(document.querySelector('.a-class')) {
  // do something
}

Much more performant option below (notice the lack of a dot before a-class).

if(document.getElementsByClassName('a-class')[0]) {
  // do something
}

querySelector uses a proper matching engine like $() (sizzle) in jQuery and uses more computing power but in 99% of cases will do just fine. The second option is more explicit and tells the code exactly what to do. It's much faster according to JSBench https://jsbench.me/65l2up3t8i


C
Community

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 = "" + inputs[i][0] + "" + testFuncs[0](input) + "" + testFuncs[1](input) + "" + testFuncs[2](input) + ""; $("table").append(tr); } td { border: 1px solid black }

#idoexist
Input!!$(sel)[0]!!$(sel).length$(sel).exists()


S
Sanu Uthaiah Bollera

I just like to use plain vanilla javascript to do this.

function isExists(selector){
  return document.querySelectorAll(selector).length>0;
}

E
Eternal1

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

I find OP's original approach not only to be much more minimal but more elegant than this. Seems like overkill to write this much code when OP's method is shorter, and doesn't involve callbacks.
For simple cases - you're right. But for more complex situations involving a lot of code on both cases i think my approach is better.
In what complex situation would this approach be better than a simple if/else statement?
j
jcreamer898

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;
};

M
MAX POWER

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.


This reads as "if exists thing" instead of "if thing exists" which if($("#thing").exists(){} reads as. Also, it's not the jQuery way.
a
andy_314

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/


H
Hydrothermal

$("selector") returns an object which has the length property. If the selector finds any elements, they will be included in the object. So if you check its length you can see if any elements exist. In JavaScript 0 == false, so if you don't get 0 your code will run.

if($("selector").length){
   //code in the case
} 

"give an array" — No, it doesn't. It gives you a jQuery object (which shares some properties with an array). Your answer is essentially the same as Tim Büthe's from 2009 too.
d
ducdhm

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
    }
);

C
Community

You don't have to check if it's greater than 0 like $(selector).length > 0, $(selector).length it's enough and an elegant way to check the existence of elements. I don't think that it is worth to write a function only for this, if you want to do more extra things, then yes.

if($(selector).length){
  // true if length is not 0
} else {
  // false if length is 0
}

a
abhirathore2006

Here is the complete example of different situations and way to check if element exists using direct if on jQuery selector may or may not work because it returns array or elements.

var a = null;

var b = []

var c = undefined ;

if(a) { console.log(" a exist")} else { console.log("a doesn't exit")}
// output: a doesn't exit

if(b) { console.log(" b exist")} else { console.log("b doesn't exit")}
// output: b exist

if(c) { console.log(" c exist")} else { console.log("c doesn't exit")}
// output: c doesn't exit

FINAL SOLUTION

if($("#xysyxxs").length){ console.log("xusyxxs exist")} else { console.log("xusyxxs doesnn't exist") }
//output : xusyxxs doesnn't exist

if($(".xysyxxs").length){ console.log("xusyxxs exist")} else { console.log("xusyxxs doesnn't exist") }
    //output : xusyxxs doesnn't exist

Demo

console.log("existing id", $('#id-1').length) console.log("non existing id", $('#id-2').length) console.log("existing class single instance", $('.cls-1').length) console.log("existing class multiple instance", $('.cls-2').length) console.log("non existing class", $('.cls-3').length)


You can try $("#xysyxxs") in your debugger, you'll see that jquery doesn't return null or undefined. So the final solution would not work