How can I clone a JavaScript object except for one key?

Question

I have a flat JS object:

{a: 1, b: 2, c: 3, ..., z:26}

I want to clone the object except for one element:

{a: 1, c: 3, ..., z:26}

What's the easiest way to do this (preferring to use es6/7 if possible)?

Answer 1

There is a Destructuring assignment syntax in JavaScript that can be used

let obj = {a: 1, b: 2, c: 3, z:26};
let {b, ...rest} = obj;

// skips the "Unused variable" warning
let {b: _, ...rest} = obj;

// removes property based on the dynamic key
const dynamicKey = "b";
let {[dynamicKey]: _, ...rest} = obj;

Modern browsers already support it out of the box. See: JavaScript operator: Destructuring assignment: Rest in objects

For old browser versions there is an option to use Babel to support destructuring assignment. It will be transpiled into:

"use strict";

function _objectWithoutProperties(obj, keys) {
  var target = {};
  for (var i in obj) {
    if (keys.indexOf(i) >= 0) continue;
    if (!Object.prototype.hasOwnProperty.call(obj, i)) continue;
    target[i] = obj[i];
  }
  return target;
}

var x = { a: 1, b: 2, c: 3, z: 26 };
var b = x.b;

var y = _objectWithoutProperties(x, ["b"]);