Object.freeze

var a = [1,2,3];
var b = [...a];
if (a === b) {
  b = []
}
b.push(1)
console.log(a, b)

let c = Object.freeze([1,2,3]);
let d = c;
if (d === c) {
  d = []
}
console.log(d===c)
d.push(1)
console.log(d, c)