Javascript / Typescript rest and spread operators

To make it easier, rest and spread operator basically helps to merge all your function parameter together. In the past, we use something like

myfunction.apply(null, myAgumentList)

With rest and spread we can easily

function log(...a) {
   console.log(a);
}

log(1,2,3,4,5); // outputs [1, 2, 3, 4, 5] array

Notice we're assigning myArguments at the back. 

let myArguments = ['x', 'y', 3]

log(1,2, myArguments); // outputs [1, 2, ['x', 'y', 3]] 2 different array 

log(1,2, ...myArguments); // outputs [1, 2, 'x', 'y', 3] 1 array


Notice we're assigning myArguments at the front. 

log(...myArguments,1,2 ); // outputs [ 'x', 'y', 3, 1, 2] essentially a single array.