There are six different functions in JavaScript’s Math library for rounding floating point numbers:
- abs()
- ceil()
- floor()
- round()
- trunc()
- fround()
What is the difference between these functions?
abs()
abs() is the absolute value of a number. Mathematically speaking, it is the distance of a number from zero. As a distance cannot be negative, the absolute value is always the positive value of a number:
Math.abs(7.89012) = 7.89012
Math.abs(-7.89012) = 7.89012
ceil()
ceil() rounds up a number to the nearest integer value greater than or equal to the given number:
Math.ceil(7.1) = 8
Math.ceil(7.8) = 8
Math.ceil(-7.1) = -7
Math.ceil(-7.8) = -7
Please note that the next largest integer from -7.1 is not -8, but -7.
floor()
floor() is the counterpart to ceil(), so it rounds the given number to the next smaller or equal number to the given number:
Math.floor(7.1) = 7
Math.floor(7.8) = 7
Math.floor(-7.1) = -8
Math.floor(-7.8) = -8
round()
round() rounds the given number to the nearest whole number:
Math.round(7.1) = 7
Math.round(7.8) = 8
Math.round(-7.1) = -7
Math.round(-7.8) = -8
The function works mathematically correctly:
math.round(7.49) = 7
math.round(7.5) = 8
trunc()
Math.trunc(7.1) = 7
Math.trunc(7.8) = 7
Math.trunc(-7.1) = -7
Math.trunc(-7.8) = -7
fround()
This function is only required in special situations where you have to work with 32-bit numbers, e.g. in graphics or audio programming. It enables more precise rounding than the more general round().
Here is a more detailed explanation than is useful in this article.
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