Function trackValueOnNode

code/new-context-api/public/app.js:3124–3169

(node)

}

function trackValueOnNode(node) {
  var valueField = isCheckable(node) ? 'checked' : 'value';
  var descriptor = Object.getOwnPropertyDescriptor(node.constructor.prototype, valueField);

  var currentValue = '' + node[valueField];

  // if someone has already defined a value or Safari, then bail
  // and don't track value will cause over reporting of changes,
  // but it's better then a hard failure
  // (needed for certain tests that spyOn input values and Safari)
  if (node.hasOwnProperty(valueField) || typeof descriptor.get !== 'function' || typeof descriptor.set !== 'function') {
    return;
  }

  Object.defineProperty(node, valueField, {
    configurable: true,
    get: function () {
      return descriptor.get.call(this);
    },
    set: function (value) {
      currentValue = '' + value;
      descriptor.set.call(this, value);
    }
  });
  // We could've passed this the first time
  // but it triggers a bug in IE11 and Edge 14/15.
  // Calling defineProperty() again should be equivalent.
  // https://github.com/facebook/react/issues/11768
  Object.defineProperty(node, valueField, {
    enumerable: descriptor.enumerable
  });

  var tracker = {
    getValue: function () {
      return currentValue;
    },
    setValue: function (value) {
      currentValue = '' + value;
    },
    stopTracking: function () {
      detachTracker(node);
      delete node[valueField];
    }
  };
  return tracker;
}

function track(node) {
  if (getTracker(node)) {