JS Stitch calculator

stitches.js

var inputs = {
  swatch: {
    stitches: 20,
    length: 4 # Really any unit, as long as it's the same as target_length
  },
  pattern: {
    multiple: 6,
    plus: 2
  },
  target_length: 21  # Really any unit, as long as it's the same as swatch.length
};

function estimate(inputs) {
  var gauge = (inputs.swatch.stitches) / (inputs.swatch.length);
  console.log("using gauge: ", gauge);
  
  var est_sts = (inputs.target_length) * gauge;
  console.log("estimated stitches: ", est_sts);
  
  var est_repeats = (est_sts - inputs.pattern.plus) / inputs.pattern.multiple;
  console.log("estimated repeats: ", est_repeats);
  
  return {
    target_sts: est_sts,
    lower: (Math.floor(est_repeats) * inputs.pattern.multiple) + inputs.pattern.plus,
    upper: (Math.ceil(est_repeats) * inputs.pattern.multiple) + inputs.pattern.plus
  };
};