Function stringify

test/angular/1.5/angular.js:12446–12461

(value)

    }

    function stringify(value) {
      if (value == null) { // null || undefined
        return '';
      }
      switch (typeof value) {
        case 'string':
          break;
        case 'number':
          value = '' + value;
          break;
        default:
          value = toJson(value);
      }

      return value;
    }

    // TODO: this is the same as the constantWatchDelegate in parse.js
    function constantWatchDelegate(scope, listener, objectEquality, constantInterp) {