A JavaScript function to find short rational number representations of floating point numbers, with the help of some continued fractions.

float2rat.js

function float2rat(x) {
    var tolerance = 1.0E-6;
    var h1=1; var h2=0;
    var k1=0; var k2=1;
    var b = x;
    do {
        var a = Math.floor(b);
        var aux = h1; h1 = a*h1+h2; h2 = aux;
        aux = k1; k1 = a*k1+k2; k2 = aux;
        b = 1/(b-a);
    } while (Math.abs(x-h1/k1) > x*tolerance);
    
    return h1+"/"+k1;
}