JavaScript: Push into an Array inside an Object?

Question

Questions:

1. How can I push an Array into another Array located inside an Object?

Example Coding:

var myObj = {
 arrayOne: [],
 arrayTwo: []
};
var arrayLetters = ['A', 'B'];
/************************************ 
obj[arrayOne].push(arrayLetters); 
RESULT
 { 
 arrayOne: [['A', 'B']], 
 arrayTwo: [] 
 };
************************************/

Comments:

Essentially, I would like to have an key index for my various arrays.

Answer 1

obj.arrayOne.push(arrayLetters);

or

obj['arrayOne'].push(arrayLetters);