JavaScript – How to Remove a Property from an Object

javascriptobjectproperties

Given an object:

let myObject = {
  "ircEvent": "PRIVMSG",
  "method": "newURI",
  "regex": "^http://.*"
};

How do I remove the property regex to end up with the following myObject?

let myObject = {
  "ircEvent": "PRIVMSG",
  "method": "newURI"
};

Best Answer

To remove a property from an object (mutating the object), you can do it by using the delete keyword, like this:

delete myObject.regex;
// or,
delete myObject['regex'];
// or,
var prop = "regex";
delete myObject[prop];

Demo

var myObject = {
  "ircEvent": "PRIVMSG",
  "method": "newURI",
  "regex": "^http://.*"
};
delete myObject.regex;

console.log(myObject);

For anyone interested in reading more about it, Stack Overflow user kangax has written an incredibly in-depth blog post about the delete statement on their blog, Understanding delete. It is highly recommended.

If you'd like a new object with all the keys of the original except some, you could use destructuring.

Demo

let myObject = {
  "ircEvent": "PRIVMSG",
  "method": "newURI",
  "regex": "^http://.*"
};

// assign the key regex to the variable _ indicating it will be unused
const { regex: _, ...newObj } = myObject;

console.log(newObj);   // has no 'regex' key
console.log(myObject); // remains unchanged

Related Solutions

JavaScript – How to Remove a Property from an Object

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];

JavaScript – How to Remove Property by Value from Object

That would probably be delete :

delete obj['option1'];

FIDDLE

To do it by value, you'd do something like :

function deleteByVal(val) {
    for (var key in obj) {
        if (obj[key] == val) delete obj[key];
    }
}

deleteByVal('item1');

FIDDLE

Best Answer

Related Solutions

JavaScript – How to Remove a Property from an Object

JavaScript – How to Remove Property by Value from Object

Related Question