Post
Ask Question

JavaScript Array Methods In ES6

Introduction

 
In this blog, we are going to learn about the new array functions, like flat(), flatMap(), reduceRight(), and copyWithin().
 

flat()

 
The flat() method creates a new array with all sub-array items merged into it up to specified depth.
 
Syntax
 
const flatArr = arr.flat([depth]) //depth will be specific up to what extent array needs to flatten.
 
Note: depth is optional
 
Example 1
  1. const arr=['a','b',['c','d']]  
  2. arr.flat(1)) or arr.flat()  
  3. //['a','b','c','d']  
Example 2
 
For a flat array of unknown depth:
  1. const arr =['a','b',['c',[[[[['d']]]]]]   
  2. arr.flat(Infinity)  
  3. //['a','b','c','d']   

flatMap()

 
The flatMap() method is the combination of map() and flat() functions. It will map all the elements of an array, then flatten those into a new array. 
 
Syntax
 
const flatMapArr = arr.flatMap(function callback(currentValue,Index,Array))
 
Note: currentValue= input array elements
 
Index= index of input array element(optional)
 
Array=it is used when array map is called(optional)
 
Example
  1. const arr1 = ['a','b','c']  
  2. const arr2 =[1,2,3]  
  3. arr1.flatMap((val,index)=>[val,arr2[index]]);  
  4. //['a',1,'b,2,'c',3]  

reduceRight()

 
The reduceRight() method reduces the array into a single value and executes the provided function on each item of the array (from right-left); the returned result from function is stored in the accumulator.
 
Syntax
 
array.reduceRight(function(total, currentValue, currentIndex, arr), initialValue)
 
Note: function(total,currentValue, currentIndex,arr) Required.
 
initialValue is optional 
 
Example
  1. const arr1=['o','l','l','e','h']  
  2. arr1.reduceRight((c,v) =>c+v);  
  3. //"hello"   

copyWithin()

 
The copyWithin() method copies a specified part of an array to a specified location within the same array and returns it without changing the length.
 
Syntax
 
array.copyWithin(target,start,end)
 
Note:target: The index position to copy the elements to (required)
 
start: The index position to start copying elements from (optional)
 
end: The index position to stop copying elements (optional)
 
Example 1
  1. const arr1=['a','b','c','d']  
  2. arr1.copyWithin(0)   
  3. //['a','b','c','d']  
Example 2
  1. const arr1=['a','b','c','d']  
  2. arr1.copyWithin(2)  
  3. //['a','b','a','b']  
Example 3
  1. const arr1=['a','b','c','d']  
  2. arr1.copyWithin(0,3)  
  3. //['d','b','c','d']  
Note
 
These array functions are only supported in modern web browsers.