# JavaScript Round To Nearest Number

11th April 2009

The JavaScript Math.round() function will round a decimal to the nearest whole number, but I found that I needed was to round a number to the nearest 10. So after a bit of thinking I realised that I could divide the value by 10, round it using the round() function and then multiply the result by 10.

So taking it a step further I decided to create a function that would round a number to the nearest 10, 100, 1000 or whatever value is entered. If this value is less than 0 then do the reverse by multiplying and dividing the number by the given value of accuracy. Here is the function.

`function roundNearest(num, acc){    if ( acc < 0 ) {        num *= acc;        num = Math.round(num);        num /= acc;        return num;    } else {        num /= acc;        num = Math.round(num);        num *= acc;        return num;    }}`

Here are some tests of the function.

`alert( roundNearest(12345, 1000) ); // 1200alert( roundNearest(12345.1234, -100) ); //12345.12`

This function can be simplified a little by putting all of the calculations onto one line.

`function roundNearest(num, acc){    if ( acc < 0 ) {        return Math.round(num*acc)/acc;    } else {        return Math.round(num/acc)*acc;    } }`