How to remove a property from an object?

Question

Currently an event is set on checkboxes, and event.target gives me the status (checked = true/false) of checkbox which is clicked.

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; } 

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

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

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

Answer 1

Using delete:

delete selectedMap[event.target.id]; 

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; } 

In fact, you could:

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:

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.)

So for me, I do this:

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

...and of course:

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

Answer 2

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 [].

You can use delete to remove an object property like so

delete selectedMap[event.target.id];