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Format Decimal with toFixed()

Published at25 Jul 2026
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JavaScript Functions Easy 0 views
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Write a JavaScript function that takes a decimal number and a number of decimal places, and returns the number formatted with exactly that many decimal places as a string using toFixed(). The toFixed() method formats a number using fixed-point notation.

Number.prototype.toFixed() is a JavaScript-specific method that rounds a number to a specified number of decimal places and returns the result as a string. Unlike toPrecision() which formats to a specified total number of significant digits, toFixed() guarantees exactly n digits after the decimal point, padding with zeros if necessary.

The toFixed() method handles rounding automatically: 1.236.toFixed(2) returns "1.24". It also handles edge cases like very large numbers (returns exponential notation for numbers outside the safe integer range). The result is a string, not a number, because formatted output often requires leading/trailing zeros that would be lost in numeric representation.

Time complexity is O(1) as the operation is performed by the JavaScript engine's internal number formatting routines. The method is widely supported in all modern JavaScript environments.

Edge cases include negative numbers (the minus sign is preserved), zero decimal places (returns an integer as string), very large or very small numbers, and ensuring the returned type is string.

Example Input & Output

Example 1
Input
10,1
Output
10.0
Explanation

Integer with 1 decimal

Example 2
Input
0.001,2
Output
0.00
Explanation

Rounded down

Example 3
Input
2.71828,4
Output
2.7183
Explanation

Rounded up

Example 4
Input
3.14159,2
Output
3.14
Explanation

Pi rounded to 2 decimals

Example 5
Input
1.5,3
Output
1.500
Explanation

Padded with zeros to 3 decimals

Algorithm Flow

Recommendation Algorithm Flow for Format Decimal with toFixed()
Recommendation Algorithm Flow for Format Decimal with toFixed()

Solution Approach

function solution(num, digits) {
  return num.toFixed(digits);
}

Best Answers

javascript - Approach 1
function solution(num, digits) {
  return num.toFixed(digits);
}