react-tween/lib/mergeDiff.js

Tween animation for React components

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.default = mergeDiff;
// Merge newKeys and oldKeys based on shared pivot keys
// By convention, oldKeys precede newKeys
//
// Example
// oldKeys    [1] 2 [3 4]   6 [8]
// newKeys        2       5 6     7
// mergedKeys  1  2  3 4  5 6  8  7
function mergeDiff(oldStyles, newStyles) {
  var prefixSlice = [];
  var slice = prefixSlice;
  var slices = Object.keys(oldStyles).reduce(function (result, k) {
    if (Object.prototype.hasOwnProperty.call(newStyles, k)) {
      slice = [];
      result[k] = slice; // eslint-disable-line no-param-reassign
    } else {
      slice.push(k);
    }
    return result;
  }, {});

  return Object.keys(newStyles).reduce(function (result, k) {
    result.push(k);
    if (Object.prototype.hasOwnProperty.call(slices, k)) {
      result = result.concat(slices[k]); // eslint-disable-line no-param-reassign
    }
    return result;
  }, prefixSlice.slice());
}