Javascript Number Formatting

Question

Certainly a stupid question, please forgive me. My customer wants decimal numbers to display with five digits. For example: 100.34 or 37.459. I was accomplishing this with val.toPrecision (5);; however, when my numbers get really small, I stop getting what I want. For example, if my number is 0.000347, it displays 0.00034700. Now, I understand why it's doing this, but what I don't know is how to get it to display 0.0003. Any thoughts?

• mrk: Check out stackoverflow.com/questions/610406/… and the first answer's sprintf link

Answer 1

Math.round(0.000347 * 1e4) / 1e4

Or with toFixed:

Number.prototype.toNDigits = function (n) {
 return (Math.abs(this) < 1) ?
 this.toFixed(n - 1) :
 this.toPrecision(n);
};

http://jsfiddle.net/HeQtH/6/

Answer 2

Our problem is with numbers less than 1 obviously. So catch them and deal them separately

function SetPrecisionToFive(n){ 
 return (n > 1) ? n.toPrecision (5) : (Math.round(n * 1e4) / 1e4).toString();
}

Answer 3

You can use the toFixed method to accomplish this. For example: (0.000347).toFixed(4)

• Michael Myers: Will toFixed change 100.34298 to 100.34 as he wants?
• katspaugh: jQuery for toFixed, are you kidding?
• James Allardice: Why would you need to be using jQuery to use toFixed?
• codeandcloud: oh pal. just leave jquery once in a while :)
• Nathan: You should totally drop that and use jQuery.

Answer 4

The Javascript toFixed() function will truncate small numbers to a fixed decimal precision, eg:

var num = .0000350;
var result = num.toFixed(5); // result will equal .00003

• katspaugh: Now do (100.34).toFixed(5).
• Kyle: @katspaugh this code snippet would be conditional... not meant to cover all cases