Javascript 如何从对象中删除属性？
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How to remove a property from an object?
提问by Rachel
Currently an event is set on checkboxes, and event.targetgives me the status (checked = true/false)of checkbox which is clicked.
当前在 上设置了一个事件checkboxes，并event.target为我提供了status (checked = true/false)单击的复选框。
I am maintaining an object which keeps the track on all the selected checkboxes
我正在维护一个对象，该对象将跟踪所有选定的复选框
var selectedMap = {};
if(event.target == true){
var key = event.target.id;
var val = event.target.name;
selectedMap[key] = val;
}
and I want to remove the element from the map which is unselected
我想从地图中删除未选中的元素
else if(event.target == false){
selectedMap.remove(event.target.id);
}
when I run this it gives me error in Firebug: selectedMap.remove is not a function
当我运行它时，它给了我以下错误Firebug：selectedMap.remove is not a function
So my question is How can I remove the element when the checkbox is unselected ?
所以我的问题是如何在未选中复选框时删除元素？
回答by T.J. Crowder
Using delete:
使用delete：
delete selectedMap[event.target.id];
You're setting the value incorrectly, though. Here's the correct way:
但是，您设置的值不正确。这是正确的方法：
if(event.target == true){
var key = event.target.id; // <== No quotes
var val = event.target.name; // <== Here either
selectedMap[key] = val;
}
In fact, you could:
事实上，你可以：
if(event.target == true){
selectedMap[event.target.id] = event.target.name;
}
Getting the event target stuff out of the way, it's easier to envision this with simple strings:
去掉事件目标的东西，用简单的字符串更容易想象这一点：
var obj = {};
obj.foo = "value of foo";
alert(obj.foo); // alerts "value of foo" without the quotes
alert(obj["foo"]); // ALSO alerts "value of foo" without the quotes, dotted notation with a literal and bracketed notation with a string are equivalent
delete obj.foo; // Deletes the `foo` property from the object entirely
delete obj["foo"]; // Also deletes the `foo` property from the object entirely
var x = "foo";
delete obj[x]; // ALSO deeltes the `foo` property
When using a plain object like this, I always use a prefix on my keys to avoid issues. (For instance, what would happen if your target element's ID was "toString"? The object already has an [inherited] property called "toString" and things would get Very Weird Very Quickly.)
当使用像这样的普通对象时，我总是在我的键上使用前缀以避免出现问题。（例如，如果你的目标元素的 ID 是“toString”会发生什么？该对象已经有一个名为“toString”的[继承]属性，事情会很快变得非常奇怪。）
So for me, I do this:
所以对我来说，我这样做：
if(event.target == true){
selectedMap["prefix" + event.target.id] = event.target.name;
}
...and of course:
...而且当然：
delete selectedMap["prefix" + event.target.id];
回答by Russ Cam
What you have is an object and not an array (although an array is an object). You declare an object literal with {}whereas an array literal is declared with [].
你拥有的是一个对象而不是一个数组（尽管数组是一个对象）。您使用 声明对象文字，{}而使用 声明数组文字[]。
You can use deleteto remove an object property like so
您可以delete像这样删除对象属性
delete selectedMap[event.target.id];
