Explain spread operator in JavaScript?

The spread operator expands an expression in places where multiple argument/variables/elements are needed to present. It represents with three dots (…).

For example:

var mid = [3, 4];

var newarray = [1, 2, ...mid, 5, 6];

console.log(newarray);

// [1, 2, 3, 4, 5, 6]

In above example, instead of appending mid array, it rather expands in the newarray with the help of spread operator. This is how spread operator works in JavaScript.