arr1 = []
for (let i = 0; i < 1000000; i++) {
arr1.push(i);
}
arr2 = [...arr1]
arr1 = []
for (let i = 0; i < 1000000; i++) {
arr1.push(i);
}
arr2 = Array.prototype.slice.apply(arr1)
arr1 = []
for (let i = 0; i < 1000000; i++) {
arr1.push(i);
}
arr2 = [...arr1.slice(0, arr1.length)]