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The three dots represent the spread operator in ES6. It allows us to do quite a few things in JavaScript:
Concatenate arrays
var shooterGames = ['Call of Duty', 'Far Cry', 'Resident Evil'];
var racingGames = ['Need For Speed', 'Gran Turismo', 'Burnout'];
var games = [...shooterGames, ...racingGames];
console.log(games) // ['Call of Duty', 'Far Cry', 'Resident Evil', 'Need For Speed', 'Gran Turismo', 'Burnout']
Destructuring an array
var shooterGames = ['Call of Duty', 'Far Cry', 'Resident Evil'];
var [first, ...remaining] = shooterGames;
console.log(first); //Call of Duty
console.log(remaining); //['Far Cry', 'Resident Evil']
Combining two objects
var myCrush = {
firstname: 'Selena',
middlename: 'Marie'
};
var lastname = 'my last name';
var myWife = {
...myCrush,
lastname
}
console.log(myWife); // {firstname: 'Selena',
// middlename: 'Marie',
// lastname: 'my last name'}
There's another use for the three dots which is known as Rest Parameters and it makes it possible to take all of the arguments to a function in as one array.
Function arguments as array
function fun1(...params) {
}