Underscore.js _.memoize() Function

Last Updated : 24 Nov, 2021

The _.memoize() function is used to memorize a given function by caching the result computed by the function. It is used to speed up for the slow running process. Syntax:

_.memoize(function, [hashFunction])

Parameters: This function accepts two parameters as mentioned above and described below:

function: The function that need to be executed.
hashFunction: It is an optional parameter. The hashFunction is used to compute the hash key for storing the result.

Return Value: It returns the result of the called function. Below examples illustrate the _.memoize 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 fib = _.memoize(function (n) {
            return n < 2 ? n : fib(n - 1) + fib(n - 2);
        });

        console.log(fib(15));
    </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 sum = _.memoize(function (n) {
            return n < 1 ? n : n + sum(n - 1);
        });

        console.log('Sum of first 10 natural number: ' + sum(10));
    </script>
</body>

</html>