Underscore.js _.fnull() Method

The _.fnull() method returns a function that protects the given function from receiving non-existing values. When the fnull() function receives a non-existing value, default safe value is returned. 

Syntax:

_.fnull( function, default );

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

• function: It is a given function that contains return logic.
• default: The value that is used when the method receives a non-existing value

Return Value: This method returns a function.

Note: This will not work in normal JavaScript because it requires the underscore.js contrib library to be installed. 

underscore.js contrib library can be installed using npm install underscore-contrib –save.

Example 1: In this example, when undefined is passed, the function returns the default safe value.

Javascript

// Defining underscore contrib variable
var _ = require('underscore-contrib');

function func(val) {
    return val;
}

safeVal = _.fnull(func, "GeeksforGeeks");

console.log(safeVal(undefined));

Output:

GeeksforGeeks

Example 2: when the existing value is passed default value is not used.

Javascript

// Defining underscore contrib variable
var _ = require('underscore-contrib');

function func(val) {
    return val;
}

safeVal = _.fnull(func, "GeeksforGeeks");

console.log(safeVal("GFG"));

Output:

GFG

Example 3: This method can also be used for integers.

Javascript

// Defining underscore contrib variable
var _ = require('underscore-contrib');

function func(val) {
    return val;
}

safeVal = _.fnull(func, 10);

console.log(safeVal(null));

Output:

10