We can use the Spread operator to expand an array into all its elements. unpacking all the array elements into one.
Example :
const arr = [7,8,9]console.log(...newArr);
const badArr = [1,2,arr[0],arr[1],arr[2]]
console.log(badArr); //1,2,7,8,9
//using spread operator
const newArr = [1,2, ...arr];
console.log(newArr);//1,2,7,8,9
console.log(...newArr); // 1 2 7 8 9 // without comma invidually
The spread (...) syntax allows an iterable, such as an array or string, to be expanded in places where zero or more arguments (for function calls) or elements (for array literals) are expected.
The spread operator is a bit similar to destructuring. The big difference is the … operator takes all the element from the array and it also doesn’t creates a new variable. and as a consequence, we can only use this where we would otherwise write values separated by a comma.
Copy an array
///copy array
const arr = [1,2,3,4,5]
const copyArr = [...arr]; //copy of arr
copyArr.push(6);
//copyArr becomes 1,2,3,4,5,6
//arr remains unafected
concatenate arrays
let arr = ["a", "b", "c"];
let array = ["d", "e", "f"];
// Append all items from array onto arr
arr = arr.concat(array);
With spread syntax this becomes:
let arr = ["a", "b", "c"];
let array = ["d", "e", "f"];
arr = [...arr, ...array];
// arr is now ["a","b","c","d","e","f"]
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