Is there an "exists" function for jQuery?

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.

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 */ }

You could use this:

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

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

How do I test whether an element exists?

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();

Using jQuery

If you are someone strongly committed to using the jQuery library, you can use the .inArray( ) method.

If the function finds the value, it returns the index position of the value and -1 if it doesn't.
 

Syntax

jQuery.inArray(search-value, array-or-string-in-which-to-search);

Code

//code to check if a value exists in an array using jQuery
<script type = 'text/javascript' >

var fruits_arr = ['Apple', 'Mango', 'Grapes', 'Orange', 'Fig', 'Cherry'];
var text = "Watermelon";

// Searching in Array
console.log('Index : ' + jQuery.inArray('Fig', fruits_arr));
console.log('Index : ' + jQuery.inArray('Peach', fruits_arr));

// Searching in String variable
console.log('Index : ' + jQuery.inArray("m", text));

</script>

Output

Index : 4
Index : -1
Index : 5