function for extracting a token value and replacing with some string

format.js

  extractFormatAndReplace: function(fmt, name, replaceCb) {
    var regxp = new RegExp('%\\(\\s*' + name + '+:(.+)\\s*\\)s');
    if (!fmt) return '';
    return fmt.replace(regxp, function findAndReplace(wholeString, match) {
      return fmt.replace(wholeString, replaceCb(wholeString, match));
    });
  }
  extractFormatAndReplace('%(hello:ValueToRetrieve)s', 'hello', function ReplaceStringWith() { return ''; });