Ext.util.Format.round doen't work properly

[lutiayi]

REQUIRED INFORMATIONExt version tested:

• Ext 4.2.0.663

Browser versions tested against:

• IE8
• Chrome

The result that was expected:

• 1.2601

The result that occurs instead:

• 1.26

Test Case:

    Ext.util.Format.round(1.26005,4)

[mitchellsimoens]

Thanks for the report.

[Animal]

Javascript's IEEE 754 number format is notoriously inaccurate at representing fractional values.

To round 1.25005, the first step is

1.26005 * 10000

Which Javascript tells us is

12600.499999999998

So when you round that, and divide back down, it ends up as 1.26

I will do some research on workarounds.

[eric.cook]

I've never liked using Math.round. The following function works for 1.26005.

function betterRound(value, precision) {
   var result = Number(value),
        adjust = 0.5;

   if (typeof precision === 'number') {
      precision = Math.pow(10, precision);
      adjust = adjust / precision;
      result = Math.floor((value + adjust) * precision) / precision;
   }
   return result;
}

[Animal]

try

Ext.util.Format.round = function(value, precision) {
    var result = Number(value),
        fraction = result.toString().split('.')[1],

    // If there is a fraction, top it up.
    // So 3.14 gets 0.004999999999 added to it to ensure no loss of data
    increment = fraction ? .4999999999 * Math.pow(10, -fraction.length) : 0;

    if (typeof precision == 'number') {
        precision = Math.pow(10, precision);
        result = Math.round((value + increment) * precision) / precision;
    }
    return result;
};

[Animal]

Yes, probably better to ditch Math.round, and just do it in code as Eric suggested.

I'll open a ticket with this suggestion as an improvement.