Checkpoints 09 - Value vs. Reference

1번 - After the following code runs, what will be the value of x?

var x = 2;
var y = x;
y = 3;

 

2
3
Not Sure

 

2번 - After the following code runs, what will be the value of x.foo?

var x = { foo: 3 };
var y = x;
y.foo = 2;

2
3
Not Sure

 

3번 - After the following code runs, what will be the value of x.foo?

var x = { foo: 3 };
var y = x;
y = 2;

2
3
undefined
Reference Error

 

4번 - After the following code runs, what will be the value of myArray?

var myArray = [2, 3, 4, 5];
var ourArray = myArray;
ourArray = [];

[ ]
[2, 3, 4, 5]
undefined

3번재쭐은 새로운 배열을 ourArray에 할당/ myArray변화 없음

 

5번 - After the following code runs, what will be the value of myArray?

var myArray = [2, 3, 4, 5];
var ourArray = myArray;
ourArray[2] = 25;
ourArray = undefined;

[ ]
[2, 3, 4, 5]
undefined
[2, 3, 25, 4, 5]
[2, 3, 25, 5]

 

 

6번 - After the following code runs, what will be the value of myArray?

var myArray = [2, 3, 4, 5];
function doStuff(arr) {
arr[2] = 25;
}

doStuff(myArray);

[ ]
[2, 3, 4, 5]
undefined
[2, 3, 25, 4, 5]
[2, 3, 25, 5]

 

7번 - After the following code runs, what will be the value of myArray?

var myArray = [2, 3, 4, 5];
function doStuff(arr) {
arr = [ ];
}

doStuff(myArray);

[ ]
[2, 3, 4, 5]
undefined
[2, 3, 25, 4, 5]
[2, 3, 25, 5]

arr이라는 내부변수에 새로운 배열을 할당

myArr가 전달된게 아니라 주소가 전달되어서 주소의 내용이 변경되지 않으면 myArray는 동일하다.

8번 - After the following code runs, what will be the value of player.score?

var player = { score: 3 };
function doStuff(obj) {
obj.score = 2;
obj = undefined;
}

doStuff(player);

2
3
undefined
Not sure

같은곳을 바라보는곳의 score 변경

obj = undefined;를 할당(player를 바라보다가 새로운곳으로)

 

9번 - After the following code runs, what will be the value of player?

var player = { score: 3 };

function doStuff(obj) {
obj = {};
}

player = doStuff(player);

 

{ score: 3 }
{ }
undefined
Not Sure

 

doStuff함수가 player를 넣어서 실행하게될경우 빈객체로 만들어버림

player는 undefined 가 들어감 (리턴값이 없어서)

 

10번 - After the following code runs, what will be the value of example?

var obj = { 
inner: { x: 10 }
};
var example = obj.inner;
obj.inner = undefined;

{ inner: { x: 10 } }
{ x: 10 }
10
undefined
Not Sure

 

obj.inner를 값을 변경해줘도 example는 변경안됨