I'm trying to create a javascript function that can take a fraction input string such as '3/2' and convert it to decimal—either as a string '1.5' or number 1.5
function ratio(fraction) {
var fraction = (fraction !== undefined) ? fraction : '1/1',
decimal = ??????????;
return decimal;
});
Is there a way to do this?
Since no one has mentioned it yet there is a quick and dirty solution:
var decimal = eval(fraction);
Which has the perks of correctly evaluating all sorts of mathematical strings.
eval("3/2") // 1.5
eval("6") // 6
eval("6.5/.5") // 13, works with decimals (floats)
eval("12 + 3") // 15, you can add subtract and multiply too
People here will be quick to mention the dangers of using a raw eval but I submit this as the lazy mans answer.
Here is the bare bones minimal code needed to do this:
var a = "3/2";
var split = a.split('/');
var result = parseInt(split[0], 10) / parseInt(split[1], 10);
alert(result); // alerts 1.5
JsFiddle: http://jsfiddle.net/XS4VE/
Things to consider:
- division by zero
- if the user gives you an integer instead of a fraction, or any other invalid input
- rounding issues (like 1/3 for example)
Something like this:
bits = fraction.split("/");
return parseInt(bits[0],10)/parseInt(bits[1],10);
I created a nice function to do just that, everything was based off of this question and answers but it will take the string and output the decimal value but will also output whole numbers as well with out errors
https://gist.github.com/drifterz28/6971440
function toDeci(fraction) {
fraction = fraction.toString();
var result,wholeNum=0, frac, deci=0;
if(fraction.search('/') >=0){
if(fraction.search('-') >=0){
wholeNum = fraction.split('-');
frac = wholeNum[1];
wholeNum = parseInt(wholeNum,10);
}else{
frac = fraction;
}
if(fraction.search('/') >=0){
frac = frac.split('/');
deci = parseInt(frac[0], 10) / parseInt(frac[1], 10);
}
result = wholeNum+deci;
}else{
result = fraction
}
return result;
}
/* Testing values / examples */
console.log('1 ',toDeci("1-7/16"));
console.log('2 ',toDeci("5/8"));
console.log('3 ',toDeci("3-3/16"));
console.log('4 ',toDeci("12"));
console.log('5 ',toDeci("12.2"));
I have a function I use to handle integers, mixed fractions (including unicode vulgar fraction characters), and decimals. Probably needs some polishing but it works for my purpose (recipe ingredient list parsing).
Inputs "2 1/2", "2½", "2 ½", and "2.5" will all return 2.5. Examples:
var numQty = require("numeric-quantity");
numQty("1 1/4") === 1.25; // true
numQty("3 / 4") === 0.75; // true
numQty("¼" ) === 0.25; // true
numQty("2½") === 2.5; // true
numQty("¾") === 0.75; // true
numQty("⅓") === 0.333; // true
numQty("⅔") === 0.667; // true
One thing it doesn't handle is decimals within the fraction, e.g. "2.5 / 5".
If you don't mind using an external library, math.js offers some useful functions to convert fractions to decimals as well as perform fractional number arithmetic.
console.log(math.number(math.fraction("1/3"))); //returns 0.3333333333333333
console.log(math.fraction("1/3") * 9) //returns 3<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjs/3.20.1/math.js"></script>Too late, but can be helpful:
You can use Array.prototype.reduce instead of eval
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce
ES6
const fractionStrToDecimal = str => str.split('/').reduce((p, c) => p / c);
console.log(fractionStrToDecimal('1/4/2')); // Logs 0.125
console.log(fractionStrToDecimal('3/2')); // Logs 1.5
CJS
function fractionStrToDecimal(str) {
return str.split('/').reduce((p, c) => p / c);
}
console.log(fractionStrToDecimal('1/4')); // Logs 0.25
[EDIT] Removed reducer initial value and now the function works for numerators greater than 1. Thanks, James Furey.
To convert a fraction to a decimal, just divide the top number by the bottom number. 5 divided by 3 would be 5/3 or 1.67. Much like:
function decimal(top,bottom) {
return (top/bottom)
}
Hope this helps, haha
It works with eval() method but you can use parseFloat method. I think it is better! Unfortunately it will work only with that kind of values - "12.2" not with "5/8", but since you can handle with calculation I think this is good approach!
If you want to use the result as a fraction and not just get the answer from the string, a library like https://github.com/infusion/Fraction.js would do the job quite well.
var f = new Fraction("3/2");
console.log(f.toString()); // Returns string "1.5"
console.log(f.valueOf()); // Returns number 1.5
var g = new Fraction(6.5).div(.5);
console.log(f.toString()); // Returns string "13"
Function (ES6):
function fractionToDecimal(fraction) {
return fraction
.split('/')
.reduce((numerator, denominator, i) =>
numerator / (i ? denominator : 1)
);
}
Function (ES6, condensed):
function fractionToDecimal(f) {
return f.split('/').reduce((n, d, i) => n / (i ? d : 1));
}
Examples:
fractionToDecimal('1/2'); // 0.5
fractionToDecimal('5/2'); // 2.5
fractionToDecimal('1/2/2'); // 0.25
fractionToDecimal('10/5/10'); // 0.2
fractionToDecimal('0/1'); // 0
fractionToDecimal('1/0'); // Infinity
fractionToDecimal('cat/dog'); // NaN
Also a bit late to the party, but an alternative to eval() with less security issues (according to MDN at least) is the Function() factory.
var fraction = "3/2";
console.log( Function("return (" + fraction + ");")() );
This would output the result "1.5" in the console.
Also as a side note: Mixed fractions like 1 1/2 will not work with neither eval() nor the solution with Function() as written as they both stumble on the space.
safer eval() according to MDN
const safeEval = (str) => {
return Function('"use strict";return (' + str + ")")();
}
safeEval("1 1/2") // 1.5
This too will work:
let y = "2.9/59"
let a = y.split('')
let b = a.splice(a.indexOf("/"))
console.log(parseFloat(a.join('')))
a = parseFloat(a.join(''))
console.log(b)
let c = parseFloat(b.slice(1).join(''))
let d = a/c
console.log(d) // Answer for y fraction
来源：https://stackoverflow.com/questions/7142657/convert-fraction-string-to-decimal