Adjust decimal format to retain two decimal places_javascript skills

During the development process, we often encounter the need to adjust the format of decimals, such as retaining two decimal places, etc. The method is also quite common, the memo is as follows.

The first method 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

Second, js1.5 and above can use toFixed(x), which can specify the number to intercept x digits 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

Both of the above The method is the most general, but it cannot meet some special requirements, such as retaining two decimal places. If it is less than two decimal places, zeros will be added if it is less than two decimal places. At this point there is a third method.

The third type is the conversion function. This code comes from a foreign forum.

Copy code The code 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//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