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JavaScript Number toPrecision() Method

The JavaScript Number toPrecision() method is used to retrieve a string representing this number to the specified precision, or it formatted the input number to the specified precision. The Precision describes the number of digits that are used to express a value.

If the value of the 'precision' parameter is not within the range of [0, 100], a 'RangeError' exception will be thrown. The same output is returned if no 'precision' parameter value is specified for this method.

Note: If the precision value is greater than the total number of digits, extra zeros will be added at the end of the number.

Syntax

Following is the syntax of JavaScript Number toPrecision() method −

toPrecision(precision)

Parameters

This method takes an optional parameter called 'precision', which is explained below −

  • precision (optional) − An integer specifying the number of significant digits.

Return value

This method returns a formetted number to the specified precision.

Example 1

The JavaScript number toPrecision() method formats a number to a specified precision or length. If the precision value is omitted, the number is returned as it is.

<html>
<head>
<title>JavaScript toPrecision() Method</title>
</head>
<body>
<script>
   const val = 10.34543;
   document.write("Given value = ", val);
   document.write("<br>Result = ", val.toPrecision());
</script>
</body>
</html>

Output

The above program returns "10.34543" in the output −

Given value = 10.34543
Result = 10.34543

Example 2

The Number toPrecision() method formats the input value to the specified precision if the 'precision' parameter value is passed to it.

<html>
<head>
<title>JavaScript toPrecision() Method</title>
</head>
<body>
<script>
   const val = 123.3454;
   const p1 = 3;
   const p2 = 5;
   const p3 = 12;
   document.write("Given value = ", val);
   document.write("<br>Precision values are = ", p1, ", ", p2, " and ", p3);
   document.write("<br>Formatted result1 = ", val.toPrecision(p1));
   document.write("<br>Formatted result2 = ", val.toPrecision(p2));
   document.write("<br>Formatted result3 = ", val.toPrecision(p3));
</script>
</body>
</html>

Output

The above program formats the input value according to the specified precision.

Given value = 123.3454
Precision values are = 3, 5 and 12
Formatted result1 = 123
Formatted result2 = 123.35
Formatted result3 = 123.345400000

Example 3

If the value of the optional parameter 'precision' is not in the range of [1, 100], this method throws a 'RangeError' exception.

<html>
<head>
<title>JavaScript toPrecision() Method</title>
</head>
<body>
<script>
   const val = 123;
   const precision = 101;
   document.write("Given value = ", val);
   document.write("<br>Precision value = ", precision);
   try {
      document.write("<br>Result = ", val.toPrecision(precision));
   } catch (error) {
      document.write("<br>", error);
   }
</script>
</body>
</html>

Output

The above program throws a 'RangeError' exception as −

Given value = 123
Precision value = 101
RangeError: toPrecision() argument must be between 1 and 100
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