Javascript 舍入数到最接近的 0.5
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Javascript roundoff number to nearest 0.5
提问by Johnydep
Can someone give me an idea how can i round off a number to the nearest 0.5.
I have to scale elements in a web page according to screen resolution and for that i can only assign font size in pts to 1, 1.5 or 2 and onwards etc.
有人可以告诉我如何将数字四舍五入到最接近的 0.5。
我必须根据屏幕分辨率缩放网页中的元素，为此我只能将 pts 中的字体大小指定为 1、1.5 或 2 等。
If i round off it rounds either to 1 decimal place or none. How can i accomplish this job?
如果我四舍五入，则四舍五入到小数点后 1 位或无。我怎样才能完成这项工作？
回答by newtron
Write your own function that multiplies by 2, rounds, then divides by 2, e.g.
编写自己的函数，乘以 2，舍入，然后除以 2，例如
function roundHalf(num) {
return Math.round(num*2)/2;
}
回答by Michael Deal
Here's a more generic solution that may be useful to you:
这是一个更通用的解决方案，可能对您有用：
function round(value, step) {
step || (step = 1.0);
var inv = 1.0 / step;
return Math.round(value * inv) / inv;
}
round(2.74, 0.1)= 2.7
round(2.74, 0.1)= 2.7
round(2.74, 0.25)= 2.75
round(2.74, 0.25)= 2.75
round(2.74, 0.5)= 2.5
round(2.74, 0.5)= 2.5
round(2.74, 1.0)= 3.0
round(2.74, 1.0)= 3.0
回答by Julia Savinkova
Math.round(-0.5)returns 0, but it should be -1according to the math rules.
Math.round(-0.5)返回0，但根据数学规则它应该是-1。
More info: Math.round()and Number.prototype.toFixed()
更多信息：Math.round()和Number.prototype.toFixed()
function round(number) {
var value = (number * 2).toFixed() / 2;
return value;
}
回答by mekdigital
function roundToTheHalfDollar(inputValue){
var percentile = Math.round((Math.round(inputValue*Math.pow(10,2))/Math.pow(10,2)-parseFloat(Math.trunc(inputValue)))*100)
var outputValue = (0.5 * (percentile >= 25 ? 1 : 0)) + (0.5 * (percentile >= 75 ? 1 : 0))
return Math.trunc(inputValue) + outputValue
}
I wrote this before seeing Tunaki's better response ;)
我在看到 Tunaki 更好的回应之前写了这个 ;)
回答by Ronan Stoffers
To extend the top answer by newtron for rounding on more than only 0.5
扩展 newtron 的最高答案，以仅对 0.5 以上进行四舍五入
function roundByNum(num, rounder) {
var multiplier = 1/(rounder||0.5);
return Math.round(num*multiplier)/multiplier;
}
console.log(roundByNum(74.67)); //expected output 74.5
console.log(roundByNum(74.67, 0.25)); //expected output 74.75
console.log(roundByNum(74.67, 4)); //expected output 76
回答by Blazes
var f = 2.6;
var v = Math.floor(f) + ( Math.round( (f - Math.floor(f)) ) ? 0.5 : 0.0 );
