MDN's Definition for forEach and map Methods

• forEach() method executes a provided function once for each array element.
• map() method creates a new array populated with the results of calling a provided function on every element in the calling Array.

			
					const grp = [0,1,2,3,4,5];

			
	

			
	
			

		
	

forEach() mutates the original data and has no return value.

			
					const newGrp= grp.forEach(num => num * 4);

console.log(newGrp); // undefined

			
	

			
	
			

		
	

On the other hand, map() does not mutate the original data. It returns a new array.

			
					const newGrp = grp.map(num => num * 4);

console.log(newGrp) // [ 0,4,8,12,16,20 ]

			
	

			
	
			

		
	

Note

• forEach is more performant when compared to map is less performant.
• return value for forEach is undefined while map returns new Array.

forEach() may be preferable when you’re not trying to change the data in your array.

References

• Array.prototype.forEach() - JavaScript | MDN
• Array.prototype.map() - JavaScript | MDN