index.js
function expandMapping(config, options) {
  var len = config.files.length, i = -1;
  var res = [];

  while (++i < len) {
    var raw = config.files[i];
    var node = new RawNode(raw, config, this);
    this.emit('files', 'rawNode', node);
    this.emit('rawNode', node);
    if (node.files.length) {
      res.push.apply(res, node.files);
    }
  }
  config.files = res;
  return config;
}
function expandMapping(config, options) {
  var len = config.files.length, i = -1;
  var res = [];

  while (++i < len) {
    var raw = config.files[i];
    var node = new RawNode(raw, config, this);
    this.emit('files', 'rawNode', node);
    this.emit('rawNode', node);
    if (node.files.length) {
      res.push.apply(res, node.files);
    }
  }
  config.files = res;
  return config;
}
function expandMapping ( config , options ) { var len = config . files . length , i = - 1 ; var res = [ ] ; while ( ++ i < len ) { var raw = config . files [ i ] ; var node = new RawNode ( raw , config , this ) ; this . emit ( 'files' , 'rawNode' , node ) ; this . emit ( 'rawNode' , node ) ; if ( node . files . length ) { res . push . apply ( res , node . files ) ; } } config . files = res ; return config ; }
Iterate over a files array and expand src-dest mappings

```js
{ files: [ { src: [ '*.js' ], dest: 'dist/' } ] }
```
@param {Object} `config`
@param {Object} `options`
@return {Object}
Iterate over a files array and expand src - dest mappings