[Javascript] 배열, for문

var arrays = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10];

for(var i=0; i < arrays.length; i++) {
    console.log(arrays[i]);
}

for(var i in arrays) {
    console.log(arrays[i]);
}

var obj1 = {
    id  :   'yujin',
    age :   '10'
}

for(var key in obj1) {
    console.log(key + " : " + obj1[key]);
}


console.log("========================");


var obj2 = {
    id  :   'yujin',
    age :   '10',
    method: function() {
        console.log('method');
    }
}

for(var key in obj2) {
    console.log(key + " : " + obj1[key]);
}



결과 ==================================
id : yujin
age : 10
=========================
id : yujin
age : 10
method : undefined