Underscore.js _.cat() Method

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The _.cat() method is used to concatenate zero or more arguments into one array.

Syntax:

_.cat(arg1, arg2, ...)

Parameters:

Args: This method accepts n arguments to concatenate into a single array.

Return Value: This method returns a concatenated array.

Note: This method 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 concatenate 2 arrays.

Javascript

// Defining underscore contrib variable 
var _ = require('underscore-contrib');  
  
// Array1 
var arr1 = [1,2,3] 
  
// Array2 
var arr2 = [4,5,6] 
  
// Concatenation 
var arr = _.cat(arr1, arr2);  
console.log("array 1 : "+ arr1);  
console.log("array 2 : "+ arr2);  
console.log("concatenated array : "+ arr);  

Output:

array 1 : 1,2,3
array 2 : 4,5,6
concatenated array : 1,2,3,4,5,6

Example 2: In this example, we will concatenate 2 numbers to form an array.

Javascript

// Defining underscore contrib variable 
var _ = require('underscore-contrib');  
  
// Number 1 
var num1 = 1 
  
// Number 2 
var num2 = 4 
  
// Concatenation 
var arr = _.cat(num1, num2);  
console.log("num1 : "+ num1);  
console.log("num2 : "+ num2);  
console.log("concatenated array : "+ arr);  

Output:

num1 : 1
num2 : 4
concatenated array : 1,4

Example 3: In this example, we will concatenate 3 arrays.

Javascript

// Defining underscore contrib variable 
var _ = require('underscore-contrib');  
// Array1 
var arr1 = [1,2,3] 
// Array2 
var arr2 = [4,5,6] 
// Array3 
var arr3 = [7,8,9] 
// Concatenation 
var arr = _.cat(arr1, arr2, arr3);  
console.log("array 1 : "+ arr1);  
console.log("array 2 : "+ arr2);  
console.log("array 3 : "+ arr3); 
console.log("concatenated array : "+ arr);  

Output:

array 1 : 1,2,3
array 2 : 4,5,6
array 3 : 7,8,9
concatenated array : 1,2,3,4,5,6,7,8,9

Example 4: The _.cat() method will also work with the arguments object as if it were an array.

Javascript

// Defining underscore contrib variable 
var _ = require('underscore-contrib');  
  
// Function 
function f(){ return _.cat(arguments, 4, 5, 6); } 
  
console.log("Array is : " + f(1,2,3));

Output:

Array is : 1,2,3,4,5,6

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