Underscore.js _.comparator() Method

The _.comparator() method takes a binary predicate-like function and returns a comparator function which can be used as a callback for the _.sort() method etc.

Syntax:

_.comparator( function );

Parameters: 

• function: a predicate-like function defined.

Return Value: This method returns a comparator 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: Sorting using a comparator function.

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

let gfgFun = function (x, y) {
    // Returns -1, 0 or 1
    return x <= y;
};

// Array
let arr = [4, 8, 2, 9, 1];

let comp = _.comparator(gfgFun);
// Using comparator function with _.sort() method
arr.sort(comp);

console.log("Sorted Array :", arr)

Output:

Sorted Array : [ 1, 2, 4, 8, 9 ]

Example 2: Reverse Sorting using a comparator function.

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

let gfgFun = function (x, y) {
    // Returns -1, 0 or 1
    return x >= y;
};

// Array
let arr = [4, 8, 2, 9, 1];

let comp = _.comparator(gfgFun);
// Using comparator function with _.sort() method
arr.sort(comp);

console.log("Sorted Array :", arr)

Output:

Sorted Array : [ 9, 8, 4, 2, 1 ]