code: function (data) {
      return this.fields.reduce(function (output, field) {
        var replacement = ''
        var placeholder = field.placeholder
        var width = field.width
  
        if (field.prefix) {
          output += field.prefix
        }
        if (placeholder) {
          replacement = data[placeholder] || ''
          if (width && (placeholder === 'hash' || placeholder === 'chunkhash')) {
            replacement = replacement.slice(0, width)
          }
          output += replacement
        }
  
        return output
      }, '')
    }
docs: Applies data to this template and outputs a filename.
  
  @param Object data