/**
* @param num The number to round
* @param precision The number of decimal places to preserve
*/
function roundUp(num, precision) {
precision = Math.pow(10, precision)
return Math.ceil(num * precision) / precision
}
roundUp(192.168, 1) //=> 192.2
rounding - How to round up a number to a precision of tenths in JavaScript? - Stack Overflow
Why not always use Math.round instead of Math.floor?
Well, they are two different functions, with two different uses. Math.floor() always rounds down to the nearest integer, while Math.round() will round up or down depending on what side of .5 the number falls on. So, the basic answer is that you use which one gets the result you expect.
When it comes to generating random numbers though, Math.floor() has a more even distribution than Math.round(). If you want to generate a random number between 0 and 2, take the following examples:
Math.floor(Math.random() * 3). Here, 0-0.999999 will give you 0, 1.0 to 1.999999 will give you 1, and 2.0 to 2.999999 will give you 2. Every number has a 33% chance of being the result.
Math.round(Math.random() * 2). Here, 0-0.499999 will give you 0, 0.5 to 1.499999 will give you 1, and 1.5 to 1.999999 will give you 2. Note that the range of numbers that lead to a 1 is twice as big as those that lead to 0 or 1. That is 25% chance of 0, 50% chance of 1, and 25% chance of 2.
rounding - How to round float numbers in javascript? - Stack Overflow
How to Round to the Nearest Integer in JavaScript
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/**
* @param num The number to round
* @param precision The number of decimal places to preserve
*/
function roundUp(num, precision) {
precision = Math.pow(10, precision)
return Math.ceil(num * precision) / precision
}
roundUp(192.168, 1) //=> 192.2
Normal rounding will work with a small tweak:
Math.round(price * 10)/10
and if you want to keep a currency format, you can use the Number method .toFixed()
(Math.round(price * 10)/10).toFixed(2)
Though this will make it a String =)
When I read through the code of colleagues and public repos, I see Math.floor used like 20x more often than Math.round.
But why? Isn't Math.round more accurate than Math.floor? Shouldn't it be the other way around (using Math.round more often than Math.floor)?
Is Math.floor so much faster than Math.round or am I missing something?
Edit
I am aware that those two do different things. My point is that in my experience, Math.floor is much too often used, when Math.round would simply be more accurate.
Well, they are two different functions, with two different uses. Math.floor() always rounds down to the nearest integer, while Math.round() will round up or down depending on what side of .5 the number falls on. So, the basic answer is that you use which one gets the result you expect.
When it comes to generating random numbers though, Math.floor() has a more even distribution than Math.round(). If you want to generate a random number between 0 and 2, take the following examples:
Math.floor(Math.random() * 3). Here, 0-0.999999 will give you 0, 1.0 to 1.999999 will give you 1, and 2.0 to 2.999999 will give you 2. Every number has a 33% chance of being the result.
Math.round(Math.random() * 2). Here, 0-0.499999 will give you 0, 0.5 to 1.499999 will give you 1, and 1.5 to 1.999999 will give you 2. Note that the range of numbers that lead to a 1 is twice as big as those that lead to 0 or 1. That is 25% chance of 0, 50% chance of 1, and 25% chance of 2.
Math.floor - You have a rating system of stars, and you aren't breaking them up into half stars. You do a query to get all the votes and the math comes back to 4.7 stars. You would use Math.floor here so that you display 4 stars.
Math.ceil - You have a slider module that displays 3 slides at a time. This module contains 19 slides. 19/3 = 6.33. If you were to floor or round here you would end up with 6. But to make sure that all 19 slides are shown, you need 7 containers, so you use Math.ceil.
Math.round - Anytime you need the closest number without worrying about anything like the above scenarios.