JavaScripts magic three dots

const obj1 = { key1: 1, key2: 2 }; const obj2 = { ...obj1, key3: 3 }; console.log(obj2); // output: { key1: 1, key2: 2, key3: 3 } const obj3 = { ...obj1, key2: 4, key3: 3 }; console.log(obj3) // output: { key1: 1, key2: 4, key3: 3 } // keys will be overridden const arr1 = [ 1, 2, 3, 4 ]; const arr2 = [ ...arr1, 5, 6 ]; console.log(arr2); // output: [ 1, 2, 3, 4, 5, 6 ] function spread(a, b, ...remaining) { console.log(remaining); } spread(1, 2, 3, 4, 5); // output: [ 3, 4, 5 ] spread(...arr1); // output: [ 3, 4 ]