Underscore.js _.compose() Function

Last Updated : 25 Nov, 2021

The _.compose() function is used to return the composition of the list of functions. The list of the function returns the value of the function that follows. Syntax:

_.compose(*functions)

Parameters: This function accept a single parameter as mentioned above and described below:

functions: It contains the list of function that to be executed.

Return Value: It returns the composition of list of functions. Below examples illustrate the _.compose() function in Underscore.js: Example 1:

html

<!DOCTYPE html>
<html>

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

<body>
    <script type="text/javascript">
        var fun1 = function (addString) {
            return "Welcome to " + addString;
        };

        var fun2 = function (GFG) {
            return GFG;
        };
        var str = _.compose(fun1, fun2);

        console.log(str('GeeksforGeeks'));
    </script>
</body>

</html>

Output:

Example 2:

html

<!DOCTYPE html>
<html>

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

<body>
    <script type="text/javascript">
        var fun1 = function (str1) {
            return 'Welcome' + str1 +
                '\nA computer science portal';
        };

        var fun2 = function (str2) {
            return ' to ' + str2.toLowerCase();
        };
        var str = _.compose(fun1, fun2);

        console.log(str('GEEKSFORGEEKS'));
    </script>
</body>

</html>