JavaScript: Format a number up to specified decimal places

JavaScript Math: Exercise-5 with Solution

Format Number to Decimal Places

Write a JavaScript function to format a number up to specified decimal places.

Test Data :
console.log(decimals(2.100212, 2));
console.log(decimals(2.100212, 3));
console.log(decimals(2100, 2));
"2.10"
"2.100"
"2100.00"

Visual Presentation:

Sample Solution:

JavaScript Code:

 // Define a function named decimals that takes two parameters: n (number) and d (number of decimal places).
function decimals(n, d) {
    // Check if both n and d are of type number, otherwise return false.
    if ((typeof n !== 'number') || (typeof d !== 'number'))
        return false;
    // Convert n to a floating-point number, defaulting to 0 if conversion fails.
    n = parseFloat(n) || 0;
    // Return the number n formatted to have d decimal places using the toFixed method.
    return n.toFixed(d);
}

// Output the result of formatting the number 2.100212 with 2 decimal places to the console.
console.log(decimals(2.100212, 2));
// Output the result of formatting the number 2.100212 with 3 decimal places to the console.
console.log(decimals(2.100212, 3));
// Output the result of formatting the number 2100 with 2 decimal places to the console.
console.log(decimals(2100, 2));

Output:

2.10
2.100
2100.00

Explanation:

In the exercise above,

• The code defines a function called "decimals()" which takes two parameters: 'n' (a number) and 'd' (the number of decimal places to format).
• Inside the function:
• It first checks whether both 'n' and 'd' are of type number. If either of them is not a number, it returns 'false'.
• It then converts the input 'n' into a floating-point number using 'parseFloat', defaulting to 0 if the conversion fails.
• The function then uses the "toFixed()" method to format the number n to have 'd' decimal places.

Flowchart:

Live Demo:

See the Pen javascript-math-exercise-5 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript function that formats a number to a specified number of decimal places without using toFixed().
• Write a JavaScript function that rounds a number to a given number of decimal places and returns a string with trailing zeros if needed.
• Write a JavaScript function that handles formatting edge cases, such as very small numbers or numbers expressed in scientific notation.
• Write a JavaScript function that formats both positive and negative numbers to a specified number of decimal places consistently.

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