let myarray = [1,2,3,4,5]
// Add to the start of an array
Array.unshift(element);
myarray.unshift(100); // output 100,1,2,3,4,5
// Add to the end of an array
Array.push(element);
myarray.push(100); // output 1,2,3,4,5,100
// Add to a specified location
Array.splice(start_position, 0, new_element...);
myarray.splice(2, 0, 100,200); // output 1,2,100,200,3,4,5
// Add with concat method without mutating original array
let newArray = [].concat(element);
let newmyarray = myarray.concat(10,20);