As you may know, we can't make a copy of array in Vanila JS with the code below. (Not a library based js. That is Vanila JS.)

var drinks = ["cola","orange juice", "tea", "beer"];
var copyOfDrinks = drinks;
drinks.push("milk");
console.log(copyOfDrinks);

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");
console.log(copyOfDrinks);

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