メモ
var array1 = [1, 2, 3];
var array2 = [4, 5, 6];
//結合
var newArray = array1.concat(array2);
console.log(newArray);
=>[1, 2, 3, 4, 5, 6]
console.log(array1);
=>[1, 2, 3]
//破壊的結合
var ArrayLength = Array.prototype.push.apply(array1, array2);
console.log(ArrayLength)
=> 6
console.log(array1);
=> [1, 2, 3, 4, 5, 6]