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I need to compare the following scenarios using decimal comparison in jquery.
var a=99999999999.99;
var b=9999999999999999999
if(parseFloat(a).toFixed(2) > parseFloat(b).toFixed(2))
This always returns true. How to fix the Issue?
Some of the outputs from what I tried:
parseFloat(9874563212).toFixed(2) > parseFloat(98745632).toFixed(2) true
parseFloat(98745632).toFixed(2) > parseFloat(987456321).toFixed(2) false
parseFloat(99999999999.99).toFixed(2) > parseFloat(9999999999999999999).toFixed(2) true
parseFloat(99999999999.99).toFixed(2) > parseFloat(999999999999).toFixed(2) false
parseFloat(99999999999.99).toFixed(2) > parseFloat(9999999999999).toFixed(2) false
parseFloat(99999999999.99).toFixed(2) > parseFloat(99999999999999).toFixed(2) false
parseFloat(99999999999.99).toFixed(2) > parseFloat(999999999999999).toFixed(2) false
parseFloat(99999999999.99).toFixed(2) > parseFloat(9999999999999999).toFixed(2) true
parseFloat(99999999999.99).toFixed(2) > parseFloat(1111111111111111).toFixed(2) true
parseFloat(99999999999.99).toFixed(2) > parseFloat(111111111111111).toFixed(2) true
780
To compare decimal numbers with JavaScript, we can round both numbers and then compare them. to multiply a and b by 100 and call Math.round with the returned number to get rid of the decimals. Then we use > to compare them. Since a is smaller than b, the console log should log false.
But why is that? In JavaScript all numbers are IEEE 754 floating point numbers. Due to the binary nature of their encoding, some decimal numbers cannot be represented with perfect accuracy. This is analagous to how the fraction 1/3 cannot be accurately represented with a decimal number with a finite number of digits.
You decide to cut decimals after 2 positions, for example, and multiply the number by 100 to remove the decimal part. Use 10000 instead of 100 to keep 4 decimal positions. Download my free JavaScript Handbook!
A better solution proposed by one of reader. Decimals will cause a big problem, especially the subtraction of decimal numbers. If you are not noticed a problem like this in live projects, this will create a big problem between the client and the software vendor. Many programming languages had these kinds of problems.
You are comparing strings, not numbers (.toFixed() returns a string). Try:
if (parseFloat(parseFloat(a).toFixed(2)) > parseFloat(parseFloat(b).toFixed(2)))
Or, if a and b are already numbers, as in your example
if (parseFloat(a.toFixed(2)) > parseFloat(b.toFixed(2)))
Or better
if (Math.round(a * 100) > Math.round(b * 100))
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