javascript JS四舍五入到小数点后两位
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JS round to 2 decimal places
提问by user2344148
I am trying to limit the returned number to be only 2 decimal places but this code isn't working for me;
我试图将返回的数字限制为只有 2 个小数位，但此代码对我不起作用；
function myFunction() {
var x = document.getElementById("mySelect").value;
document.getElementById("demo").innerHTML = "Result is: " + x * 1.09; value = valToRound.toFixed(2);
}
}
What am I doing wrong?
我究竟做错了什么？
回答by Paul
Typing in the JS Browser console
在 JS 浏览器控制台中输入
x = 2.71828
x.toFixed(2)
"2.72"
it is clear that .toFixed(2)works
很明显.toFixed(2)有效
What you did wrong was rounding afterprinting the answer, and not using the correct variables.
您做错的是在打印答案后四舍五入，而不是使用正确的变量。
document.getElementById("demo").innerHTML = "Result is: " + x * 1.09; value = valToRound.toFixed(2);
It is also a good idea to get in the habit of converting strings to numbers with parseFloat(). In JS, '2'*'2' is '4' but '2'+'2' is '22', unless you first convert to number.
养成将字符串转换为数字的习惯也是一个好主意parseFloat()。在 JS 中，'2'*'2' 是 '4' 但 '2'+'2' 是 '22'，除非您先转换为数字。
If you do it this way it will work:
如果您这样做，它将起作用：
function myFunction() {
var x = parseFloat(document.getElementById("mySelect").value);
var valToRound = x * 1.09;
var value = valToRound.toFixed(2);
document.getElementByID("demo").innerHTML = "Result is: " + value;
}
