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JavaScript | Math.round( ) function
  • Last Updated : 14 Mar, 2018

The Math.round() function in JavaScript is used to round the number passed as parameter to its nearest integer.
Syntax

Math.round(value)

    Parameters :

  • The number to be rounded to its nearest integer.

    Returns :

  • Result after rounding the number passed as a parameter to the function passed as parameter.



    Below are some examples to illustrate the Math.round() function:

    1. Rounding Off a number to its nearest integer: To round off a number to its nearest integer, the math.round() function should be implemented in the following way:






      <script type="text/javascript">
          var round =Math.round(5.8);
          document.write("Number after rounding : " + round); 
      </script>

      Output:

      Number after rounding : 6
    2. Rounding Off a negative number to its nearest integer: The Math.round() function itself rounds off a negative number when passed as parameter to it. To round off a negative number to its nearest integer, the Math.round() function should be implemented in the following way:




      <script type="text/javascript">
          var round =Math.round(-5.8);
          document.write("Number after rounding : " + round); 
      </script>

      Output:

      Number after rounding : -6
    3. Math.round() function, when parameter has “.5” as decimal: Below program shows the result of Math.round() function when the parameter has “.5” in decimal.




      <script type="text/javascript">
          var round =Math.round(-12.5);
          document.write("Number after rounding : " + round);
          var round =Math.round(12.51);
          document.write("Number after rounding : " + round); 
      </script>

      Output:

      Number after rounding : -12
      Number after rounding : 13

    Errors and Exceptions
    1. A non-numeric string passed as parameter returns NaN
    2. An array with more than 1 integer passed as parameter returns NaN
    3. An empty variable passed as parameter returns NaN
    4. An empty string passed as parameter returns NaN
    5. An empty array passed as parameter returns NaN

    Below are some examples that illustrate the Math.floor() function in JavaScript:




    <!-- NEGATIVE NUMBER EXAMPLE -->
    <script type="text/javascript">
        document.write(Math.round(-2)); 
        document.write(Math.round(-2.56));          
    </script>

    Output:

    -2
    -3
    




    <!-- POSITIVE NUMBER EXAMPLE -->
    <script type="text/javascript">
        document.write(Math.round(2)); 
        document.write(Math.round(2.56));          
    </script>

    Output:

    2
    3
    




    <!-- STRING EXAMPLE -->
    <script type="text/javascript">
        document.write(Math.floor("Geeksforgeeks"));          
    </script>

    Output:

    NaN
    




    <!-- ADDITION INSIDE FUNCTION EXAMPLE -->
    <script type="text/javascript">
        document.write(Math.floor(7.2+9.3));           
    </script>

    Output:

    17
    

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