jQuery.inArray( value, array [, fromIndex ] )Returns: Number
Description: Search for a specified value within an array and return its index (or -1 if not found).
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version added: 1.2jQuery.inArray( value, array [, fromIndex ] )
The $.inArray() method is similar to JavaScript's native .indexOf() method in that it returns -1 when it doesn't find a match. If the first element within the array matches value, $.inArray() returns 0.
Because JavaScript treats 0 as loosely equal to false (i.e. 0 == false, but 0 !== false), to check for the presence of value within array, you need to check if it's not equal to (or greater than) -1.
The comparison between values is strict. The following will return -1 (not found) because a number is being searched in an array of strings:
$.inArray( 5 + 5, [ "8", "9", "10", 10 + "" ] );
Example:
Report the index of some elements in the array.
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>jQuery.inArray demo</title>
<style>
div {
color: blue;
}
span {
color: red;
}
</style>
<script src="https://code.jquery.com/jquery-3.5.0.js"></script>
</head>
<body>
<div>"John" found at <span></span></div>
<div>4 found at <span></span></div>
<div>"Karl" not found, so <span></span></div>
<div>"Pete" is in the array, but not at or after index 2, so <span></span></div>
<script>
var arr = [ 4, "Pete", 8, "John" ];
var $spans = $( "span" );
$spans.eq( 0 ).text( jQuery.inArray( "John", arr ) );
$spans.eq( 1 ).text( jQuery.inArray( 4, arr ) );
$spans.eq( 2 ).text( jQuery.inArray( "Karl", arr ) );
$spans.eq( 3 ).text( jQuery.inArray( "Pete", arr, 2 ) );
</script>
</body>
</html>