Underscore.js _.negate() Function

Last Updated : 25 Nov, 2021

Underscore.js is a JavaScript library that provides a lot of useful functions that help in the programming in a big way like the map, filter, invoke, etc even without using any built-in objects.

The _.negate() function is an inbuilt function in Underscore.js library of JavaScript which is used to find a new negated version of the stated predicate function.

Syntax:

_.negate(predicate)

Parameters: It accepts a single parameters which is specified below:

predicate: It is the stated predicate function.

Return Value: This method returns a new negated version of the stated predicate function.

Example 1:

javascript

<!DOCTYPE html>
<html>

<head>
    <script src=
"https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js">
    </script>
</head>

<body>
    <script>
        var isNaN = _.negate(Boolean);
        
        console.log(_.find(
            [3, -11, undefined, 41, 0], isNaN));
    </script>
</body>

</html>

Output:

undefined

Example 2:

javascript

<!DOCTYPE html>
<html>

<head>
    <script src=
"https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.9.1/underscore-min.js">
    </script>
</head>

<body>
    <script>
        function isCSportal(character) {
            return character === "GeeksforGeeks";
        }

        var isNotCSportal = _.negate(isCSportal);
        console.log(isNotCSportal("GeeksforGeeks"));
        console.log(isNotCSportal("GfG"));
    </script>
</body>

</html>