如何从对象中删除属性？ [英] How to remove a property from an object?

问题描述

目前在复选框上设置了一个事件， event.target 给了我单击复选框的status（checked = true / false）。

我正在维护一个对象，该对象保留所有选中复选框的轨道

I am maintaining an object which keeps the track on all the selected checkboxes

var selectedMap  = {};

if(event.target == true){
    var key = event.target.id;
    var val = event.target.name;
    selectedMap[key] = val;
}

我希望从地图中删除未选中的元素

and I want to remove the element from the map which is unselected

else if(event.target == false){
  selectedMap.remove(event.target.id);
}

当我运行它时，它给我错误 Firebug ： selectedMap.remove不是函数

when I run this it gives me error in Firebug : selectedMap.remove is not a function

所以我的问题是 如何在取消选中复选框时删除元素？

So my question is How can I remove the element when the checkbox is unselected ?

推荐答案

使用删除：

delete selectedMap[event.target.id];

但是，您设置的值不正确。这是正确的方法：

You're setting the value incorrectly, though. Here's the correct way:

if(event.target == true){
    var key = event.target.id;   // <== No quotes
    var val = event.target.name; // <== Here either
    selectedMap[key] = val;
}

事实上，你可以：

if(event.target == true){
    selectedMap[event.target.id] = event.target.name;
}

获取事件目标的东西，更容易设想这个简单字符串：

Getting the event target stuff out of the way, it's easier to envision this with simple strings:

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

当使用像这样的普通对象时，我总是使用我的密钥上的前缀，以避免问题。 （例如，如果您的目标元素的ID是toString会发生什么？该对象已经有一个名为toString的[inherited]属性，并且很快就会非常奇怪。）

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.)

所以对我来说，我这样做：

So for me, I do this:

if(event.target == true){
    selectedMap["prefix" + event.target.id] = event.target.name;
}

......当然还有：

...and of course:

delete selectedMap["prefix" + event.target.id];

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