ReactMap_applyChanges.js

  componentWillReceiveProps(nextProps) {
    // Prevent the diff'ing if function is
    // triggered before a style is set
    if(this.props.mapStyle === null) return;
    const map = this.map;
    
    // Remember where we are in the lifecycle here,
    // even though we already update the Redux state,
    // this component's current properties still 
    // reflect the old state:
    const oldStyle = this.props.mapStyle;
    const newStyle = nextProps.mapStyle;
    
    // Do a deep equality check first to make sure
    // an update needs to happen. Avoid unnessecary 
    // converting and diff'ing:
    if(!Immutable.is(oldStyle, newStyle)) {
      const changes = diffStyles(before.toJS(), after.toJS());
      // 'changes' will be an array of:
      // {command: '...', args: ['...', ...]}
      // objects that can be applied to the map:
      changes.forEach(function(change) {
        map[change.command].apply(map, change.args);
      });
    }
  }