As you may know, we can't make a copy of array in Vanila JS with the code below.

var drinks = ["cola","orange juice", "tea", "beer"];
var copyOfDrinks = drinks;

We see "copyOfDrinks" show the contents of "drinks" because the variable is a reference of the original array. Simple "for loop" will do the job in this case.

var drinks = ["milk","whisky"];
var copyOfDrinks = [];
for(let i = 0; i < drinks.length; i++){
copyOfDrinks[i] = drinks[i]
drinks.push("lemon juice");

In modern JS (ES6,7), they created a syntax for doing this.
var copy = [...drinks];
Reference: Spread_syntax

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