Multiply the elements of an array in JavaScript
We will be given an initial array and we have to multiply all the elements of the array with each other to find a final product.
Examples:
Input: arr = [1, 2, 3, 4, 5];
Output: 120
Explanation: 1 * 2 * 3 * 4 * 5 = 120
Input: arr = [11, 12, 13, 14, 15]
Output: 360360
Explanation: 11 * 12 * 13 * 14 * 15 = 360360
There are three ways available in which we can solve this problem in JavaScript:
Table of Content
- Recursive Method:
- Iterative Method:
- Using the in-built methods:
- Using forEach method
- Using the Math Object:
Recursive Method:
In this approach, we will recursively visit each element of the array and multiply it with the product of all the previous elements to get a new product value till the current element.
Example: The below code example will explain to you the practical implementation of the recursive approach to solve this problem in JavaScript:
const arr1 = [8, 9, 3, 7, 5, 13];
const arr2 = [12, 9, 5, 18, 23];
const recursiveMultiply = (arr, ind) => {
if (ind === arr.length - 1) {
return arr[ind];
} else {
return arr[ind] * recursiveMultiply(arr, ind + 1);
}
};
console.log(recursiveMultiply(arr1, 0));
console.log(recursiveMultiply(arr2, 0));
Output
98280 223560
Time Complexity: O(n), n is the size of the passing array.
Space Complexity: O(n), n is the size of the passing array.
Iterative Method:
In this method, we will use a simple for loop in JavaScript to iterate through the elements of the array and multiply them with each other to get the multiply result at the end. This approach is more efficient than the previous recursive approach as it takes the linear time complexity and constant extra space to solve the probelm.
Example: The below example will illustrate how you can multiply elements of an array using a loop in JavaScript:
const arr1 = [8, 9, 3, 7, 5, 13];
const arr2 = [12, 9, 5, 18, 23];
const iterativeMultiply = (arr) => {
let result = 1;
for (let i = 0; i < arr.length; i++) {
result *= arr[i];
}
return result;
};
console.log(iterativeMultiply(arr1))
Output
98280 223560
Time Complexity: O(n), n is the size of the passing array.
Space Complexity: O(1)
Using the in-built methods:
There are some in-built array methods available in JavaScript which we can use to iterate through the array elements and make changes in their values by passing a callback function inside them. We will use the map() and the reduce() in-built methods in this approach to multiply the elements of an array.
Example: The below code example will explain the use of the in-built JavaScript methods to multiply the elements of an array:
let arr1 = [8, 9, 3, 7, 5, 13];
let arr2 = [12, 9, 5, 18, 23];
let mapRes = 1;
arr1.map((currItem) => {
mapRes *= currItem;
});
const reduceRes = arr2.reduce((res, currItem) => res *= currItem);
console.log(mapRes);
console.log(reduceRes);
Output
98280 223560
Time Complexity: O(n), n is the size of the passing array.
Space Complexity: O(1)
Using forEach method
In this approach we use forEach method. With forEach we look at each number in the array, one after the other. for each number we multiply it with a running total.
Example: Below example uses forEach method to multiply the elements of an array.
function multiplyArray(arr) {
let result = 1;
arr.forEach(num => {
result *= num;
});
return result;
}
let array = [1, 2, 3, 4, 5];
console.log(multiplyArray(array));
Output
120
Time complexity: O(n)
Space complexity: O(1)
Using the Math Object:
JavaScript’s Math object provides several methods for mathematical operations. We can use the Math object to multiply all the elements of an array using the Math.pow() method, which calculates the power of a number.
Example:
function multiplyArray(arr) {
return arr.reduce((acc, curr) => acc * curr, 1);
}
const array = [1, 2, 3, 4, 5];
console.log(multiplyArray(array));
Output
120
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