JavaScript parseFloat() Function

Below is the example of the parseFloat() function.

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

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  • 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:

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    <!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>

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    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.

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    <!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>           

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    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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