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JavaScript Number toExponential() Method

The JavaScript Number toExponential() method returns a string representing this number in exponential notation. If the optional parameter 'fractionDigits' is not in the range of [0, 100], this method throws a 'RangeError' exception. Additionally, if you try to invoke this method on an object that is not a number, you will get a 'TypeError' exception.

The fraction-Digits is an integer specifying the number of digits after the decimal point. Defaults to as many digits as necessary to specify the number.

The result of the toExponential() method is a string with the following format −

sign + '1.' + mantissa + 'e' + sign + exponent

Where,

  • 'sign' is either + or - depeding on the sign of the number.
  • 'mantissa' is the fractional part of the number, rounded to fractionDigits digtis.
  • 'exponent' is the power of 10 that the number should be multiplied by

Syntax

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

toExponential(fractionDigits)

Parameters

This method accepts an optional parameter called 'fractionDigits', which is described below −

  • fractionDigits (optional) − An integer specifying the number of digits after the decimal point.

Return value

This method returns a string representing this number in exponential notation with one digit before the decimal point.

Example 1

In this example, we will demonstrate how to use the toExponential() method in JavaScript to represent a number in exponential notation.

<html>
<head>
<title>JavaScript toExponential() Method</title>
</head>
<body>
<script>
   const val = 5;
   document.write("Given value = ", val);
   document.write("<br>Number in exponential notation = ", val.toExponential());
</script>
</body>
</html>

Output

The above program returns an exponential notation as "5e+0" −

Given value = 5
Number in exponential notation = 5e+0

Example 2

If we pass 3 as the value of an optional parameter (i.e. fractionDigits), this method will represent a number in exponential notation rounded to 3 decimal places.

<html>
<head>
<title>JavaScript toExponential() Method</title>
</head>
<body>
<script>
   const val = 5.454312;
   const fractionDigits = 3;
   document.write("Given value = ", val);
   document.write("<br>Fraction digits value = ", fractionDigits);
   document.write("<br>Number in exponential notation = ", val.toExponential(fractionDigits));
</script>
</body>
</html>

Output

After executing the above program, it will return an exponential notation rounded to 3 decimal places as −

Given value = 5.454312
Fraction digits value = 3
Number in exponential notation = 5.454e+0

Example 3

If the value of the 'fractionDigits' parameter is outside the range of 0 to 100, this method will throw a "RangeError" exception.

<html>
<head>
<title>JavaScript toExponential() Method</title>
</head>
<body>
<script>
   const val = 5.34565432;
   const fractionDigits = -1;
   document.write("Given value = ", val);
   document.write("<br> Fraction Digits value = ", fractionDigits);
   try {
      document.write("<br>Number in exponential notation = ", val.toExponential(-1));
   } catch (error) {
      document.write("<br>",error);
   }
</script>
</body>
</html>

Output

The above program throws a 'RangeError' exception.

Given value = 5.34565432
Fraction Digits value = -1
RangeError: toExponential() argument must be between 0 and 100

Example 4

The Number toExponential() method throws a "TypeError" exception if we invoke this method on an object that is not a number.

<html>
<head>
<title>JavaScript toExponential() Method</title>
</head>
<body>
<script>
   const val = "abc";
   const fractionDigits = 10;
   document.write("Given value = ", val);
   document.write("<br> Fraction Digits value = ", fractionDigits);
   try {
      document.write("<br>Number in exponential notation = ", val.toExponential(-1));
   } catch (error) {
      document.write("<br>",error);
   }
</script>
</body>
</html>

Output

The above program throws a 'TypeError' exception as shown below −

Given value = abc
Fraction Digits value = 10
TypeError: val.toExponential is not a function
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