Javascript value scaling between two ranges, the correct way

range-scaling.js

function convertRange( value, r1, r2 ) { 
    return ( value - r1[ 0 ] ) * ( r2[ 1 ] - r2[ 0 ] ) / ( r1[ 1 ] - r1[ 0 ] ) + r2[ 0 ];
}

// example
convertRange(26, [0, 100], [-2, 2]);
// = -0.96

// another example
convertRange(26, [0, 100.1], [-2, 2]);
// = -0.9610389610389609

// Originally found it on https://stackoverflow.com/a/14224813/988591 (thanks Oleq!)
// It seems to work perfectly.

// The problem with the originally forked function was that it worked with integers only
// making it very imprecise when dealing with small numbers, for example:
scaleValue(26, [0, 100], [-2, 2]);
// would just return 0

// The solution in this gist uses linear interpolation, which is essential in so many situations, 
// but for some reason I keep forgetting and rediscovering it every 5 years or so... 
// Hopefully this time it will stick... ;)