I'm looking to get the scale and precision from a number in the following example.

var x = 1234.567;

I'm not seeing any .scale or .precision functions built in and I'm not sure what the best way to right one is.

I'm looking to get the scale and precision from a number in the following example.

var x = 1234.567;

I'm not seeing any .scale or .precision functions built in and I'm not sure what the best way to right one is.

• javascript
• jquery

• What are those scale and precision ? Do you mean the numbers of digits on each side of the point ? – Denys Séguret Commented Jun 8, 2012 at 16:45
• convert to a string and then do split and see the string length. – Chetter Hummin Commented Jun 8, 2012 at 16:46
• Does that make any sense with floating point? Consider 0.1 + 0.1 + 0.1. You'd expect that to be 0.3. Well it's not. It's 0.30000000000000004. Suddenly, your precision has shot up. – Eric Commented Jun 8, 2012 at 17:36
• @Eric He doesn't use the numbers for calculation. – VisioN Commented Jun 8, 2012 at 17:39
• @VisioN: Even so, there are floating point problems here. If you're not going to use numbers to calculate, store them as a string! – Eric Commented Jun 8, 2012 at 17:57

3 Answers 3

You can use Number.prototype.toFixed()

var x = 1234.56780123;
    
x.toFixed(2); // output: 1234.57
x.toFixed(3); // output: 1234.568
x.toFixed(4); // output: 1234.5680

var x = 1234.567;

var parts = x.toString().split('.');

parts[0].length; // output: 4 for 1234

parts[1].length; // output: 3 for 567

NOTE

Javascript has toPrecision() method that gives to a number with specified length.

For example:

var x = 1234.567;

x.toPrecision(4); // output: 1234

x.toPrecision(5); // output: 1234.5

x.toPrecision(7); // output: 1234.56

But

x.toPrecision(5); // output: 1235

x.toPrecision(3); // output: 1.23e+3 

and so on.

According to comment

Is there a way to check that the string contain .?

var x = 1234.567

x.toString().indexOf('.'); // output: 4

Note

.indexof() return first index of target else -1.

Another advanced solution (if I correctly understand what you mean by scale and precision):

function getScaleAndPrecision(x) {
    x = parseFloat(x) + "";
    var scale = x.indexOf(".");
    if (scale == -1) return null;
    return {
        scale : scale,
        precision : x.length - scale - 1
    };
}

var res = getScaleAndPrecision(1234.567);

res.scale;       // for scale
res.precision;   // for precision

If number is not float function returns null.