js scale like D3

js-scale

(function() {
/**
Usage:
```javascript
  var userScale = scale()
      .domain(0, 10)
      .range(0,100);
  userScale(2);
  // => 20

  userScale.range(100, 0);
  userScale(2);
  // => 80
```
*/
    function scale() {
        var domain = [];
        var range = [];

        var _scale = function(x) {
            if (domain.length < 2) {return _scale;}
            if (range.length < 2) {return _scale;}

            x = Math.max(x, domain.min);
            x = Math.min(x, domain.max);
            var x2 = distance(domain[0], x);
            var rangeVal = x2/domain.distance * range.distance;
            return range[0] + rangeVal;
        };
        function distance(x1, x2) {
            if (x1 instanceof Array) {
                x2 = x1[1];
                x1 = x1[0];
            }
            // return Math.max(x1, x2) - Math.min(x1, x2);
            return x2 - x1;
        }

        function initDistance(obj) {
            obj.distance = distance(obj);
            obj.min = Math.min.apply(Math, obj);
            obj.max = Math.max.apply(Math, obj);
            return obj;
        }
        _scale.domain = function(/* start, end */) {
            domain = Array.prototype.slice.call(arguments, 0, 2);
            initDistance(domain);
            return _scale;
        };
        _scale.range = function(/* start, end */) {
            range = Array.prototype.slice.call(arguments, 0, 2);
            initDistance(range);
            return _scale;
        };
        return _scale;
    }
});