During the development process, we often encounter formats that need to be adjusted, such as retaining the two decimal places after the decimal point, etc. The method is also quite common, please note the following.
The first one is to use math.round
var original=28.453
1) //round "original" to two decimals
var result=Math.round(original*100)/100; //returns 28.45
2) // round "original" to 1 decimal
var result=Math.round(original*10)/10; //returns 28.5
The second type, js1.5 or above can use toFixed(x) to specify the number to intercept the x position after the decimal point.
3) //round "original" to two decimals
var result=original.toFixed(2); //returns 28.45
4) // round "original" to 1 decimal
var result=original.toFixed(1); //returns 28.5
The above two methods are the most common, but they cannot meet certain special requirements. For example, keeping the two decimal places after the decimal point. If you are less than two digits, you will make up for zeros. At this time, there is a third method.
The third type is the conversion function. This code comes from a foreign forum.
The code copy is as follows:
function roundNumber(number,decimals) {
var newString;// The new rounded number
decimals = Number(decimals);
if (decimals < 1) {
newString = (Math.round(number)).toString();
} else {
var numString = number.toString();
if (numString.lastIndexOf(".") == -1) {// If there is no decimal point
numString += ".";// give it one at the end
}
var cutoff = numString.lastIndexOf(".") + decimals;// The point at which to truncate the number
var d1 = Number(numString.substring(cutoff,cutoff+1));// The value of the last decimal place that we'll end up with
var d2 = Number(numString.substring(cutoff+1,cutoff+2));// The next decimal, after the last one we want
if (d2 >= 5) {// Do we need to round up at all? If not, the string will just be truncated
if (d1 == 9 && cutoff > 0) {// If the last digit is 9, find a new cutoff point
while (cutoff > 0 && (d1 == 9 || isNaN(d1))) {
if (d1 != ".") {
cutoff -= 1;
d1 = Number(numString.substring(cutoff,cutoff+1));
} else {
cutoff -= 1;
}
}
}
d1 += 1;
}
if (d1 == 10) {
numString = numString.substring(0, numString.lastIndexOf("."));
var roundedNum = Number(numString) + 1;
newString = roundedNum.toString() + '.';
} else {
newString = numString.substring(0,cutoff) + d1.toString();
}
}
if (newString.lastIndexOf(".") == -1) {// Do this again, to the new string
newString += ".";
}
var decs = (newString.substring(newString.lastIndexOf(".")+1)).length;
for(var i=0;i<decimals-decs;i++) newString += "0";
//var newNumber = Number(newString);// make it a number if you like
document.roundform.roundedfield.value = newString; // Output the result to the form field (change for your purposes)
}
5) //round "original" to two decimals
var result=original.toFixed(2); //returns 28.45
6) // round "original" to 1 decimal
var result=original.toFixed(1); //returns 28.5
var original=28.4
var result=original.toFixed(2); //returns 28.40