In JavaScript, standard built-in object-copy operations (spread syntax, Array.prototype.concat(), Array.prototype.slice(), Array.from(), Object.assign(), and Object.create()) do not create deep copies (instead, they create shallow copies).
A deep copy of an object is a copy whose properties do not share the same references (point to the same underlying values) as those of the source object from which the copy was made.
As a result, when you change either the source or the copy, you can be assured you're not causing the other object to change too; that is, you won't unintentionally be causing changes to the source or copy that you don't expect.
That behavior contrasts with the behavior of a shallow copy, in which changes to either the source or the copy may also cause the other object to change too (because the two objects share the same references).
One way to make a deep copy of a JavaScript object, if it can be serialized, is to use JSON.stringify() to convert the object to a JSON string, and then JSON.parse() to convert the string back into a (completely new) JavaScript object:
let ingredients_list = ["noodles",{"list":["eggs","flour","water"]}];
let ingredients_list_deepcopy = JSON.parse(JSON.stringify(ingredients_list));
// Change the value of the 'list' property in ingredients_list_deepcopy.
ingredients_list_deepcopy[1].list = ["rice flour","water"]
// The 'list' property does not change in ingredients_list.
console.log(ingredients_list[1].list);
// Array(3) [ "eggs", "flour", "water" ]
Readmore: https://developer.mozilla.org/en-US/docs/Glossary/Deep_copy