JavaScript parseFloat() Function

Last Updated : 06 Jul, 2020

Below is the example of the parseFloat() function.

Example:

<script>
    var v2 = parseFloat("3.14");

    document.write('Using parseFloat("3.14") = '
    + v2 + "<br>");
</script>
Output:
```
Using parseFloat("3.14") = 3.14
```

The parseFloat() function is used to accept the string and convert it into a floating-point number. If the string does not contain a numeral value or If the first character of the string is not a Number then it returns NaN i.e, not a number. It actually returns a floating-point number parsed up to that point where it encounters a character that is not a Number.

Syntax:

parseFloat(Value)

Parameters: This function accept a single parameter as mentioned above and described below:

value This parameter ontains a string which is converted to a floating-point number.

Return value: It returns a floating-point Number and if the first character of a string cannot be converted to a number then the function returns NaN i.e, not a number.

Below examples illustrate the parseFloat() function in JavaScript:

Example 1: The parseFloat() function ignores leading and trailing spaces and returns the floating point Number of the string.

Input : var n = parseFloat("  2018  ");
Output: n=2018 (floating point Number)

Example 2:

Input: var a = parseFloat("1000.04");
Output:now a = 1000.04(floating point Number)

More example codes for the above function are as follows:

Program 1:

<!DOCTYPE html>
<html>
  
<body>
<script>
    // It ignores leading and trailing spaces.
    a = parseFloat(" 100 ")
    document.write('parseFloat(" 100 ") = ' +a +"<br>");
  
    // It returns floating point Number until
    // it encounters Not a Number character
    b = parseFloat("2018@geeksforgeeks")
    document.write('parseFloat("2018@geeksforgeeks") = '
    +b +"<br>");
  
    // It returns NaN on Non numeral character
    c = parseFloat("geeksforgeeks@2018")
    document.write('parseFloat("geeksforgeeks@2018") = '
    +c +"<br>");
  
    d = parseFloat("3.14")
    document.write('parseFloat("3.14") = '
    +d +"<br>");
  
    // It returns only first Number it encounters
    e = parseFloat("22 7 2018")
    document.write('parseFloat("22 7 2018") = '
    +e +"<br>");
      
    </script>
  
</body>
</html>

Output:

parseFloat(" 100 ") = 100
parseFloat("2018@geeksforgeeks") = 2018
parseFloat("geeksforgeeks@2018") = NaN
parseFloat("3.14") = 3.14
parseFloat("22 7 2018") = 22

Program 2: Using isNaN() function to test that converted values are valid number or not.

<!DOCTYPE html>
<html>
  
<body>
<script>
    var x = parseFloat("3.14");
    if (isNaN(x))
        document.write("x is not a number" + "<br>");
    else
        document.write("x is a number" + "<br>");
  
    var y = parseFloat("geeksforgeeks");
    if (isNaN(y))
        document.write("y is not a number" + "<br>");
    else
        document.write("y is a number" + "<br>");
  
    // Difference between parseInt() and parseFloat()
    var v1 = parseInt("3.14");
    var v2 = parseFloat("3.14");
  
    document.write('Using parseInt("3.14") = ' 
    + v1 + "<br>");
    document.write('Using parseFloat("3.14") = ' 
    + v2 + "<br>");
</script>
  
</body>
</html>           

Output:

x is a number
y is not a number
Using parseInt("3.14") = 3
Using parseFloat("3.14") = 3.14

Supported Browsers:

Google Chrome
Firefox
Internet Explorer
Safari
Opera

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