将数字截断为两位小数而不进行舍入 [英] Truncate number to two decimal places without rounding

问题描述

假设我的值为15.7784514，我想将其显示为15.77而没有舍入。

Suppose I have a value of 15.7784514, I want to display it 15.77 with no rounding.

var num = parseFloat(15.7784514);
document.write(num.toFixed(1)+"<br />");
document.write(num.toFixed(2)+"<br />");
document.write(num.toFixed(3)+"<br />");
document.write(num.toFixed(10));

结果 -

15.8
15.78
15.778
15.7784514000 

如何显示15.77？

推荐答案

将数字转换为字符串，将数字与小数点后第二位匹配：

Convert the number into a string, match the number up to the second decimal place:

function calc(theform) {
    var num = theform.original.value, rounded = theform.rounded
    var with2Decimals = num.toString().match(/^-?\d+(?:\.\d{0,2})?/)[0]
    rounded.value = with2Decimals
}

<form onsubmit="return calc(this)">
Original number: <input name="original" type="text" onkeyup="calc(form)" onchange="calc(form)" />
<br />"Rounded" number: <input name="rounded" type="text" placeholder="readonly" readonly>
</form>

toFixed 方法在某些情况下失败，与 toString 不同，所以要非常小心。

The toFixed method fails in some cases unlike toString, so be very careful with it.

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