Javascript Array forEach()

 let numbers = [1, 3, 4, 9, 8]; // function to compute square of each number function computeSquare(element) { console.log(element * element); } 
// compute square root of each element numbers.forEach(computeSquare);
 /* Output: 1 9 16 81 64 */

forEach() Syntax

The syntax of the forEach() method is:

 arr.forEach(callback(currentValue), thisArg)

Here, arr is an array.

forEach() Parameters

The forEach() method takes in:

• callback - The callback function to execute on every array element. It takes in:
  • currentValue - The current element being passed from the array.
• thisArg (optional) - Value to use as this when executing callback. By default, it is undefined.

forEach() Return Value

• Returns undefined.

Example 1: Printing Contents of Array

 function printElements(element, index) { console.log('Array Element ' + index + ': ' + element); } const prices = [1800, 2000, 3000, , 5000, 500, 8000]; // forEach does not execute for elements without values // in this case, it skips the third element as it is empty 
prices.forEach(printElements);

Output

 Array Element 0: 1800 Array Element 1: 2000 Array Element 2: 3000 Array Element 4: 5000 Array Element 5: 500 Array Element 6: 8000

Example 2: Using thisArg

 function Counter() { this.count = 0; this.sum = 0; this.product = 1; } Counter.prototype.execute = function (array) { 
 array.forEach((entry) => { this.sum += entry; ++this.count; this.product *= entry; }, this)
 } const obj = new Counter(); obj.execute([4, 1, , 45, 8]); console.log(obj.count); // 4 console.log(obj.sum); // 58 console.log(obj.product); // 1440

Output

 4 58 1440

Here, we can again see that forEach skips the empty element. thisArg is passed as this inside the definition of the execute method of the Counter object.

Also Read:

• JavaScript Array map()
• JavaScript forEach()