Underscore.js _.noop() Function

Last Updated : 10 Jul, 2020

Underscore.js is a JavaScript library that makes operations on arrays, string, objects much easier and handy. The _.noop() function is used to return "undefined" irrespective of the arguments passed to it.

Note: It is very necessary to link the underscore CDN before going and using underscore functions in the browser. When linking the underscore.js CDN The "_" is attached to the browser as global variable.

Syntax:

_.noop();

Parameters: It takes optional parameter of any type.

Return Value: This function returns the value of type undefined.

Example 1:

html

<!DOCTYPE html>
<html>

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

<body>
    <script>
        let str = new String(_.noop())
        console.log(`String is ${str}`)

        let obj = new Object(_.noop())
        console.log(`Object is ${obj.Object}`)

        let int = _.noop()
        console.log(`Integer is ${int}`)

        let arr = new Array(_.noop())
        console.log(`Array is ${arr[0]}`)
    </script>
</body>

</html>

Output:

Example 2:

html

<!DOCTYPE html>
<html>

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

<body>
    <script>
        let val = undefined;
        let val2 = _.noop();

        console.log(val === val2)

        if (val == val2)
            console.log(
                `val and val2 are equal`);
        else
            console.log(
                `val and val2 are not equal`);
    </script>
</body>

</html>

Output:

Example 3: Passing parameters to the _.noop() function.

html

<!DOCTYPE html>
<html>

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

<body>
    <script>
        let func = (para1) => {
            console.log(para1)
        }
        console.log("output: ")
        func(_.noop("some value"));

        // Pass function as parameter
        console.log("output: ")
        console.log(_.noop(func))

        console.log("output: ")
        console.log(_.noop(func()))
    </script>
</body>

</html>