Javascript piecewise function factory

piecewise.js

function Piecewise(xs, ys) {
  return function(x) {
    //bisect
    var lo = 0, hi = xs.length - 1;
    while (hi - lo > 1) {
      var mid = (lo + hi) >> 1;
      if (x < xs[mid]) hi = mid;
      else lo = mid;
    }
    //project
    return ys[lo] + (ys[hi] - ys[lo]) / (xs[hi] - xs[lo]) * (x - xs[lo]);
  };
}

Nice, It could be a small npm module.

Done: https://www.npmjs.com/package/piecewise-function

Thanks, i will use it.