JavaScript Number toPrecision() Method

1. Syntax of JavaScript Number toPrecision() Method
2. Example 1: Use the number.toPrecision() Method Without digits Parameter
3. Example 2: Use the number.toPrecision() Method With digits Parameter
4. Exceptions
5. Example 3: Use the number.toPrecision() Method With digits Values Not Between 1 to 100
6. Example 4: Invoke the number.toPrecision() Method on String Values

Users can use the number.toPrecision() method to format the Number object to particular precision. Furthermore, the method converts the Number object to a string and formats the Number object.

Syntax of JavaScript Number toPrecision() Method

let number = 23.2321;
number.toPrecision();
number.toPrecision(digits);

Parameters

digits - The digits is an optional parameter specifying the total number of digits you want to keep in the Number object string, including before and after the decimal point.

Return

The number.toPrecision() method returns the Number object in the string format after formatting to the digits precision.

Example 1: Use the number.toPrecision() Method Without digits Parameter

We have taken different positive and negative numeric values in the example below. We have used the number.toPrecision() method to format the number without the digits parameter.

In the output, users can observe that when we don’t pass the digits parameter, it returns the same Number object after converting it to a string.

let num_value1 = 123.132;
let num_value2 = -2311;
console.log(num_value1.toPrecision());
console.log(num_value2.toPrecision());

Output:

123.132
-2311

Example 2: Use the number.toPrecision() Method With digits Parameter

When we use the digits parameter with the number.toPrecision() method, it formats the number string to contain only the total digits number.

Here, we have to use the exponential notation of the number for the value3 number object, and users can see how it is formatted using the number.toPrecision() method in the example below.

Also, the number.toPrecision() method neglects the leading zero and removes it, which you can see in the output of value4.

let value1 = 1987.132432;
let value2 = -2.112;
let value3 = 123.34e+5;
let value4 = 00090;
console.log(value1.toPrecision(4));
console.log(value2.toPrecision(6));
console.log(value3.toPrecision(2));
console.log(value4.toPrecision(5));

Output:

1987
-2.11200
1.2e+7
90.000

Exceptions

Example 3: Use the number.toPrecision() Method With digits Values Not Between 1 to 100

If users follow the ECMA-262 script to format the numbers, they need a precision of up to 21 digits. Still, the number.toPrecision() method allows us to format the number up to 100 precision.

When we pass the value of digits above 100 or negative, it always returns the RangeError, which users can understand using the example below.

let value1 = 1987.132432;
let value2 = -2.112;
console.log(value1.toPrecision(300));
console.log(value2.toPrecision(-10));

Output:

RangeError: toPrecision() argument must be between 1 and 100

Example 4: Invoke the number.toPrecision() Method on String Values

The number.toPrecision() method works only with number values. If we invoke it with string or other objects, it returns TypeError.

To solve the error, users can parse the number from the string.

In the example below, we have used the string objects with the number.toPrecision() method to demonstrate the TypeError.

let value1 = "Welcome!";
let value2 = "Delft";
console.log(value1.toPrecision());
console.log(value2.toPrecision());

Output:

TypeError: value1.toPrecision is not a function

This article has demonstrated the different use cases of the number.toPrecision() method. Also, we have learned to overcome the errors and exceptions we get while using the method.