Remove a JSON attribute

javascript

prompt-engineering

functions

performance

byAnton Shumikhin·Sep 4, 2024

Eliminate an unwanted attribute from a JSON object with the delete keyword:

let jsonObj = {"name": "Jane", "age": 25};
delete jsonObj.age; // Bye bye, "age" key!

console.log(jsonObj); // Results in: { "name": "Jane" }

Swift and clean—attribute vanished.

Deletion with dynamic attribute names

In case the attribute's name isn't available upfront or held in a variable, utilize bracket notation:

let dynamicKey = "age";
delete jsonObj[dynamicKey]; // "age" key has no place in this world!

console.log(jsonObj); // Results in: { "name": "Jane" }

This method tackles those unpredictable moments when the attribute names are, well, just dynamic.

Addressing nested attributes

For nested JSON objects, removing an attribute remains as intuitive, just goes a bit deeper:

let nestedObj = {
  "user": {
    "name": "Jane",
    "details": { "age": 25, "hobby": "reading" }
  }
};

delete nestedObj.user.details.age; // The unfathomable depths of "age" are no more!

console.log(nestedObj); // Results in: { "user": { "name": "Jane", "details": { "hobby": "reading" } } }

Chiseling nested data fosters a tidier structure.

Consider immutable data and exceptions

Despite its effortless application, the delete keyword can sometimes be a tricky beast with immutable data structures like Object.freeze():

const immutableObj = Object.freeze({ "name": "Jane", "age": 25 });
delete immutableObj.age; // Oops! "age" laughs at our feeble endeavours.

console.log(immutableObj); // Results in: { "name": "Jane", "age": 25 }

In this instance, delete will fail unobtrusively, leaving the immutable object smirking. Beware of these boogie traps and verify objects are mutable beforehand.

Practical alternatives for performance

Though useful, delete can impact performance in JavaScript engines due to object shape alteration. For performance-laden code, look for alternative methods, like setting properties to undefined or rebuilding an object without the unwanted properties:

let jsonObj = { "name": "Jane", "age": 25, "hobby": "reading" };

// Option 1: Set unwanted attribute to undefined. Not a Jedi way but works.
jsonObj.age = undefined;
// Option 2: Rebuild object, excluding unwanted attribute. More elegant, isn't it?
jsonObj = { "name": jsonObj.name, "hobby": jsonObj.hobby };

console.log(jsonObj); // Results in: { "name": "Jane", "hobby": "reading" }