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I'm working on a "toy problem" where I am supposed to write a JavaScript function that converts a decimal into a fraction and returns it as a string. For example: fractionConverter(2.75) should return "11/4".
Here is my code:
function fractionConverter (number) {
if (number > 0) {
var isNegative = false;
} else if (number < 0) {
var isNegative = true;
}
number = Math.abs(number);
if (number % 1 === 0) {
var finalFrac = number + "/1";
} else {
for (var i = 2; i < 10000000000; i++) {
if ((i * number) % 1 === 0) {
var finalFrac = (i * number) + "/" + i;
}
if (finalFrac) { break; }
}
}
var getFrac = function(numString, bool) {
if (!bool) {
return numString;
} else {
return "-" + numString;
}
}
return getFrac(finalFrac, isNegative);
}
Sorry about the formatting. Anyway, I'm getting a weird spec failure. The function returns the correct values for the following numbers: 0.5, 3, 2.5, 2.75, -1.75 and .88. For some reason, however, it is failing on 0.253213. It is returning 1266065/5000000 instead of 253213/1000000. Not really sure why.
Thanks
756
I am just improving @william's answer, I think this script gives you more reduced fraction.
function fractionConverter(number) {
var fraction = number - Math.floor(number);
var precision = Math.pow(10, /\d*$/.exec(new String(number))[0].length);
var getGreatestCommonDivisor = function(fraction, precision) {
if (!precision)
return fraction;
return getGreatestCommonDivisor(precision, fraction % precision);
}
var greatestCommonDivisor = getGreatestCommonDivisor(Math.round(fraction * precision), precision);
var denominator = precision / getGreatestCommonDivisor(Math.round(fraction * precision), precision);
var numerator = Math.round(fraction * precision) / greatestCommonDivisor;
function reduce (numer,denom) {
for (var i = 2; i >= 9; i++) {
if ((numer%i===0) && (denom%i)===0) {
numerator=numer/i;
denominator=denom/i;
reduce(numerator,denominator);
};
};
}
reduce(numerator,denominator);
return numerator + "/" + denominator;
}
document.getElementById("output").innerHTML = fractionConverter(0.24888);
Here is the HTML
<body>
<p id="output"></p>
</body>
</html>
Javascript doesn't deal with floating point numbers accurately.
I tried typing this into node:
0.253213 * 1000000
And I got this:
253213.00000000003
Here is a different approach to testing for a multiplier
var bigNumber = Math.pow(10,8);
var isDivisible = (Math.round(i * number * bigNumber)/bigNumber % 1) == 0;
This will help you some of the way.
This also work the way you might expect it to, if you wanted 0.333333333 to be treated as 1/3.
One issue is that the highest integer you can have is javascript is between 10^15 and 10^16.
If ((number * bigNumber) > 2^53) this will not work.
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