I Don't Know Javascript

Spread syntax was introduced as part of Javascript in the ES2015/ECMAS-6. This allows iterable likes array, object or string to get expanded. Spread can be used in following ways: in array : [...iterableArray, 3 , 'four', 5] in object : {...iterableObj} The spread operator is very useful for concat, copying,apply, expanding, math operations,etc in array and objects. Let discuss each in detail. Concat var arr1 = [1,2,3]; var arr2 = [4,5,6]; without spread var concatenatedArray = arr1.concat(arr2); // [1,2,3,4,5,6] with spread var concatenatedArray = [...arr1, ...arr2 ] // [1,2,3,4,5,6] Copying var arr1 = [1,2,3]; var arr2 = [...arr1]; arr2.push(4); console.log(arr2); // [1,2,3,4] console.log(arr1); // [1,2,3] Replacement for apply var add = (a,b,c) => a+b+c; var arr1 = [1,2,3]; add(...arr1); // replacing add.apply(null,arr1); Expanding array var programming = ["Java", "NodeJs", "Python"]; var sub