In JavaScript, when dealing with the numbers there are specific methods to the format them according to the different precision needs. Two such methods are toFixed() and toPrecision(). These methods are part of the Number object in JavaScript and are used to the manipulate and format numbers for display or computation purposes.

What is toFixed()?

The toFixed() method in JavaScript is used to the format a number using the fixed-point notation. It rounds the number to the specified number of the decimal places and returns the result as a string.

Characteristics:

• It returns a string representation of the number.
• If the number of the decimals specified is more than the actual decimal digits zeros are added to the end.
• The original number is not modified toFixed() returns a new string.

Application:

• Useful when we need a specific number of the decimals for the display purposes such as in financial applications or when formatting data for the charts.

Example: toFixed(2) rounds num to the two decimal places and returns “123.46” as a string.

let num = 123.456789;
let formattedNum = num.toFixed(2);
console.log(formattedNum);

123.46

What is toPrecision()?

The toPrecision() method in JavaScript returns a string representing the number in the exponential or fixed-point notation depending on the input precision. It formats the number to the specified the precision in which includes significant digits.

Characteristics:

• It returns a string representation of the number.
• The precision parameter determines the total number of the significant digits.
• It can switch between the fixed-point and exponential notation based on the size of the number and the specified precision.

Applications:

• Useful when we want a specific number of the significant digits in the output.
• Often used in the scientific calculations or when we need to the maintain significant figures in data processing.

Example: toPrecision(4) formats num to the four significant digits resulting in the “123.5”.

let num = 123.456789;
let formattedNum = num.toPrecision(4);
console.log(formattedNum);

123.5

Difference Between toFixed() and toPrecision()