Floating point number precision in JavaScript

The representation of floating points in JavaScript follows the IEEE-754 format. It is a double-precision format where 64 bits are allocated for every floating point.

The displaying of these floating values could be handled using these methods: 

Using toFixed() Method

The number of decimal places in float values can be set using the toFixed() method. This method converts the number into a string, keeping the specified number of digits after the point. If no value is passed as a parameter, then it takes 0 as the default value i.e. no decimal points are displayed. 

Syntax:

number.toFixed(digits)

Example: This example shows the use of the toFixed() method.

Javascript

pi = 3.14159265359;
twoPlaces = pi.toFixed(2);
fivePlaces = pi.toFixed(5);

console.log(twoPlaces);
console.log(fivePlaces);

Output

3.14
3.14159

Using toPrecision() Method

The number of total digits in float values can be set using the toPrecision() method. This method converts the number into a string, keeping the total number of digits of the value as specified and rounding them to the nearest number. If no value is passed as a parameter, then the function acts as a toString() function effectively returning the value passed as a string. 

Syntax:

number.toPrecision(precision);

Example: This example shows the use of the toPrecision() method.

Javascript

pi = 3.14159265359;
twoPlaces = pi.toPrecision(2);
fivePlaces = pi.toPrecision(5);

console.log(twoPlaces);
console.log(fivePlaces);

Output

3.1
3.1416

Using toExponential() Method

JavaScript Number toExponential() method is used to convert a number to its exponential form. It returns a string representing the Number object in exponential notation. The toExponential() method is used with a number as shown in the above syntax using the ‘.’ operator. This method will convert a number to its exponential form.

Syntax:

number.toExponential(value)

Example: toExponential(2) represents the number 12345.6789 in exponential notation with 2 digits of precision. The output might look like 1.23e+4, where 1.23 is the significand and 4 is the exponent.

Javascript

const myNumber = 12345.6789;

// Using toExponential with precision
const exponentialNotation = myNumber.toExponential(2);

console.log(exponentialNotation);

Output

1.23e+4