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Underscore.js _.complement() Method

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The _.complement() method returns a function that reverses the sense of a given predicate function.

Syntax:

_.complement( function );

Parameters:

  • function: predicate function defined containing the returning logic.

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, we will see the use of the  _.complement() Method

javascript




// Defining underscore contrib variable
const _ = require('underscore-contrib');
 
function gfgFun(x) {
    return x >= 2;
}
 
let comp = _.complement(gfgFun);
 
let x = 3;
 
console.log("Without Complement Function:", gfgFun(x))
 
console.log("With Complement Function:", comp(x));


Output:

Without Complement Function: true
With Complement Function: false

Example 2: In this example, we will see the use of the  _.complement() Method

javascript




// Defining underscore contrib variable
const _ = require('underscore-contrib');
 
function gfgFun(x) {
    return x == "Geeks";
}
 
let comp = _.complement(gfgFun);
 
let x = "Geek";
console.log("Without Complement Function:", gfgFun(x))
 
console.log("With Complement Function:", comp(x));


Output:

Without Complement Function: false
With Complement Function: true

Last Updated : 11 Apr, 2023
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