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Finding product of Number digits in JavaScript
We are required to write a JavaScript program that takes in a number and finds the product of all of its digits.
Input Output Scenarios
Here are examples of finding the product of number digits:
Input = 12345 Output = 120 (1 × 2 × 3 × 4 × 5 = 120)
We can also work with string numbers and convert them to integers:
Input = "12345" Output = 120
Using Math.floor() and Modulo Operator
The Math.floor() function returns the largest integer less than or equal to a given number. We use it to remove the last digit by dividing by 10.
Syntax
Math.floor(x)
Example: Product of Number Digits
This approach uses Math.floor() to extract each digit and multiply them:
<!DOCTYPE html>
<html>
<head>
<title>Product of Number Digits</title>
</head>
<body>
<p id="result"></p>
<script>
let num = 12345;
let product = 1;
while (num != 0) {
product = product * (num % 10);
num = Math.floor(num / 10);
}
document.getElementById("result").innerHTML = "The product of digits is: " + product;
</script>
</body>
</html>
The product of digits is: 120
Using parseInt() with String Conversion
The parseInt() function parses a string argument and returns an integer value.
Syntax
parseInt(string)
Example: Converting String to Integer
This method converts the number to a string, then iterates through each character:
<!DOCTYPE html>
<html>
<head>
<title>Product of Number Digits</title>
</head>
<body>
<button onclick="calculateProduct()">Calculate Product</button>
<p id="output"></p>
<script>
function calculateProduct() {
let numberStr = "12345";
let product = 1;
for (let i = 0; i < numberStr.length; i++) {
product = product * parseInt(numberStr[i]);
}
document.getElementById("output").innerHTML = "Product: " + product;
}
</script>
</body>
</html>
Product: 120
Using Array Methods
A more modern approach using array methods:
function getDigitProduct(num) {
return num.toString()
.split('')
.map(Number)
.reduce((product, digit) => product * digit, 1);
}
console.log(getDigitProduct(12345)); // 120
console.log(getDigitProduct(987)); // 504
120 504
Comparison of Methods
| Method | Input Type | Performance | Readability |
|---|---|---|---|
| Math.floor() + Modulo | Number | Fast | Medium |
| parseInt() + Loop | String/Number | Medium | Good |
| Array Methods | Number | Slower | Excellent |
Conclusion
All three methods effectively calculate the product of number digits. Choose the Math.floor() approach for performance, or array methods for cleaner, more readable code.
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