Javascript 为什么$event不能与ng change一起使用？

这是我的html标记，它包含ng change事件，我将$event作为参数传递给它

 <input type="text" ng-model="dynamicField.value" ng-change="myFunction(dynamicField,$event)"/>

无论何时调用此函数，警报都会将事件的值显示为“未定义”

---

请引导我

从

angular.js

，

ngChange

指令注册

输入因用户原因发生变化时要执行的角度表达式 与输入元素的交互

该指令只是将求值表达式添加到视图更改侦听器列表中

var ngChangeDirective = valueFn({
  restrict: 'A',
  require: 'ngModel',
  link: function(scope, element, attr, ctrl) {
    ctrl.$viewChangeListeners.push(function() {
      scope.$eval(attr.ngChange);
    });
  }
});

更新

$modelValue

后，这些侦听器一次执行一个

this.$$writeModelToScope = function() {
    ngModelSet($scope, ctrl.$modelValue);
    forEach(ctrl.$viewChangeListeners, function(listener) {
      try {
        listener();
      } catch (e) {
        $exceptionHandler(e);
      }
    });
  };

正如您所看到的，没有传递任何事件，因为

ngChange

所做的只是在更新

ngModel

时执行表达式。这是确保表达式在设置模型值后运行的好方法

与

ngChange

ngClick

相反，它将

$event

传递到click handling函数中，因为它处理DOM事件

forEach(
  'click dblclick mousedown mouseup mouseover mouseout mousemove mouseenter mouseleave keydown keyup keypress submit focus blur copy cut paste'.split(' '),
  function(eventName) {
    var directiveName = directiveNormalize('ng-' + eventName);
    ngEventDirectives[directiveName] = ['$parse', '$rootScope', function($parse, $rootScope) {
      return {
        restrict: 'A',
        compile: function($element, attr) {
          // We expose the powerful $event object on the scope that provides access to the Window,
          // etc. that isn't protected by the fast paths in $parse.  We explicitly request better
          // checks at the cost of speed since event handler expressions are not executed as
          // frequently as regular change detection.
          var fn = $parse(attr[directiveName], /* interceptorFn */ null, /* expensiveChecks */ true);
          return function ngEventHandler(scope, element) {
            element.on(eventName, function(event) {
              var callback = function() {
                fn(scope, {$event:event});
              };
              if (forceAsyncEvents[eventName] && $rootScope.$$phase) {
                scope.$evalAsync(callback);
              } else {
                scope.$apply(callback);
              }
            });
          };
        }
      };
    }];
  }
);

---

在事件发生时，DOM事件对象作为

$event

，

fn（作用域，{$event:event}）传递到处理函数中
 从
angular.js
，
ngChange
指令注册

输入因用户原因发生变化时要执行的角度表达式
与输入元素的交互

该指令只是将求值表达式添加到视图更改侦听器列表中

var ngChangeDirective = valueFn({
  restrict: 'A',
  require: 'ngModel',
  link: function(scope, element, attr, ctrl) {
    ctrl.$viewChangeListeners.push(function() {
      scope.$eval(attr.ngChange);
    });
  }
});

更新
$modelValue
后，这些侦听器一次执行一个

this.$$writeModelToScope = function() {
    ngModelSet($scope, ctrl.$modelValue);
    forEach(ctrl.$viewChangeListeners, function(listener) {
      try {
        listener();
      } catch (e) {
        $exceptionHandler(e);
      }
    });
  };

正如您所看到的，没有传递任何事件，因为
ngChange
所做的只是在更新
ngModel
时执行表达式。这是确保表达式在设置模型值后运行的好方法

与
ngChange
ngClick
相反，它将
$event
传递到click handling函数中，因为它处理DOM事件

forEach(
  'click dblclick mousedown mouseup mouseover mouseout mousemove mouseenter mouseleave keydown keyup keypress submit focus blur copy cut paste'.split(' '),
  function(eventName) {
    var directiveName = directiveNormalize('ng-' + eventName);
    ngEventDirectives[directiveName] = ['$parse', '$rootScope', function($parse, $rootScope) {
      return {
        restrict: 'A',
        compile: function($element, attr) {
          // We expose the powerful $event object on the scope that provides access to the Window,
          // etc. that isn't protected by the fast paths in $parse.  We explicitly request better
          // checks at the cost of speed since event handler expressions are not executed as
          // frequently as regular change detection.
          var fn = $parse(attr[directiveName], /* interceptorFn */ null, /* expensiveChecks */ true);
          return function ngEventHandler(scope, element) {
            element.on(eventName, function(event) {
              var callback = function() {
                fn(scope, {$event:event});
              };
              if (forceAsyncEvents[eventName] && $rootScope.$$phase) {
                scope.$evalAsync(callback);
              } else {
                scope.$apply(callback);
              }
            });
          };
        }
      };
    }];
  }
);

在事件发生时，DOM事件对象作为
$event
，
fn（作用域，{$event:event}）传递到处理函数中
 与$event有什么关系？首先传递$event，然后传递自定义参数。传递
dynamicField.value
函数代替
dynamicField
与$event有什么关系？首先传递$event，然后传递自定义参数。传递
dynamicField.value
函数代替
dynamicField