Javascript 无法读取未定义的属性“目标”
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Cannot read property 'target' of undefined
提问by Alexey K
In my render method I have component
在我的渲染方法中，我有组件
<DatePicker selected={this.state.startDate} onChange={this.handleChange()}/>
handleChange is following
handleChange 如下
handleChange: function (e) {
var that = this;
console.log(e.target.value)
return function () {
that.setState({
startDate: e.target.value
});
}
},
By when I try to load page with this component, I get error
当我尝试使用此组件加载页面时，出现错误
Cannot read property 'target' of undefined
无法读取未定义的属性“目标”
What am I doing wrong ?
我究竟做错了什么 ？
回答by Matthew Barbara
The problem is that you are invoking the function in this line:
问题是您正在调用此行中的函数：
onChange={this.handleChange()}
All you have to do is simply pass the function as a value to onChange without invoking it.
您所要做的就是将函数作为值传递给 onChange 而无需调用它。
onChange={this.handleChange}
When you use parenthesis you'd be invoking a function/method instead of binding it with an event handler. Compare the following two examples:
当您使用括号时，您将调用一个函数/方法，而不是将其与事件处理程序绑定。比较以下两个例子：
//invokes handleChange() and stores what the function returns in testA.
const testA = this.handleChange()
vs
对比
//stores the function itself in testB. testB be is now a function and may be invoked - testB();
const testB = this.handleChange
回答by Andreas Bigger
If you are passing event using an arrow function, you should try the following:
如果您使用箭头函数传递事件，您应该尝试以下操作：
onChange={(e) => handleChange(e)}
回答by bennygenel
You are executing function rather than passing it as a prop.
您正在执行函数而不是将其作为道具传递。
You need to change this,
你需要改变这个，
onChange={this.handleChange()}
with this,
有了这个，
onChange={this.handleChange}
回答by Adeel Imran
Simply do this
只需这样做
<DatePicker selected={this.state.startDate} onChange={this.handleChange}/>
It will pass the event param of the function automatically. The rest of your code is okay.
它将自动传递函数的事件参数。你的其余代码没问题。
回答by Master Ace
Changing this onChange={this.handleChange}to this onChange={() => this.handleChange()}may also help if all the suggestions above don't work.
这个改变onChange={this.handleChange}这个onChange={() => this.handleChange()}也可以帮助，如果以上所有建议不起作用。
