A mutable object
Mutable is a type of variable that can be changed.
In JavaScript, only Objects and Arrays(technically a type of object) are
mutable, not primitive(immutable) values.
Immutables are the objects whose state cannot be changed once the object is
created. Boolean, Null, Undefined, Number, String, and Symbols are immutable.immutable values
let a = {
foo: 'bar'
};
let b = a;
a.foo = 'test';
console.log(b.foo); // test
console.log(a === b) // true
let a = 'test';
let b = a;
a = a.substring(2);
console.log(a) //st
console.log(b) //test
console.log(a === b) //false
let a = ['foo', 'bar'];
let b = a;
a.push('baz')
console.log(b); // ['foo', 'bar', 'baz']
console.log(a === b) // true
let a = 1;
let b = a;
a++;
console.log(a) //2
console.log(b) //1
console.log(a === b) //falsewhat is immutable
// by negative example here is how to make a javascript immutable
'use strict';
const a = Object.freeze([4, 5, 6]);
// Instead of: a.push(7, 8, 9);
const b = a.concat(7, 8, 9);
// Instead of: a.pop();
const c = a.slice(0, -1);
// Instead of: a.unshift(1, 2, 3);
const d = [1, 2, 3].concat(a);
// Instead of: a.shift();
const e = a.slice(1);
// Instead of: a.sort(myCompareFunction);
const f = R.sort(myCompareFunction, a); // R = Ramda
// Instead of: a.reverse();
const g = R.reverse(a); // R = RamdaCopyright © 2021 Codeinu
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