4.14 배열- 이중배열

<script type="text/javascript">

        /* let name = 'ingoo';

         let txt = 'hello ${name} world!'

 

         let a = 'boo';

         let b = '자바';

         let c = '스크립트';

         let str = '저는 ${}이고 ${b+c}입니다'

         console.log(str);*/

 

         //선언할 수 있습니다 배열

 

         arr = new Array(); // 이렇게

         arr = []; //이렇게

         arr = [, , , , ];

 

 

         //arr.push()의 기능 = () 안에 숫자를 넣으면 배열 마지막에 그 숫자가 배열에 추가됨

         arr = [1,2,3];

         arr.push(3) //이렇게 해주면 [1,2,3,3]

         arr.push(4) //이렇게 해주면 [1,2,3,3,4]

 

        /*console.log(arr);

 

         //arr.pop()의 기능. 마지막 값이 제거 됩니다.

         arr.pop(); //현재 상태의 array에서 pop을 쓰게 되면

         

         console.log(arr);*/ //마지막의 4 사라짐. 

 

         arr.pop();

 

         //arr.indexOf() 의 기능. 이 매서드는 현재 자주 사용하진 않지만 알아두면 유용함. 

         //인자값이 두개가 들어갑니다. 1.찾을 요소 2. 어디서부터 찾을지

         

         arr.push(4)

         arr.push(5)

         arr.push(6)

         arr.push(7)

         arr.push(8)

         arr.push(9)

         arr.push(10)

         

         // value  [1,2,3,4,5,6,7,8,9,10]

         // key 값 [0,1,2,3,4,5,6,7,8,9]

         //1.찾을 요소 2. 어디서부터 찾을 지()

         /*console.log(arr.indexOf(4,0)); //3

         console.log(arr.indexOf(4,4)); //-1 이건 찾을 수 없다 는 뜻

         console.log(arr.indexOf(4,2));*/ //3

 

        

 

        arr2 = [1,2,3,4,5,6,[1,2,3]];

        /*console.log(arr2); // [1,2,3,4,5,6,Array(3)];

        console.log(arr2[4]); //5

        console.log(arr2[6]);*/ //[1,2,3] -> 이중 배열 

 

        //3층짜리 아파트가 있는데, 한층에 4호실까지 있응

 

        arr3 = [[,,,],[,,,],[,,,]];

        /*console.log(arr3);*/ // [Array(4),Array(4),Array(4)]

 

        arr3 = [[101,102,103,104],[201,202,203,204],[301,302,303,304]];

        console.log(arr3);

 

        //104호를 찾고 싶다면

 

        // 1) 1층으로 가라

        console.log(arr3[0]); //[101,102,103,104]

        // 2) 1층에서 3번째 호실로 가라

        console.log(arr3[0][3]) // 104호

        //204호를 빼라

        arr3[1].pop();

        console.log(arr3[1]); //[201,202,203]

 

        //

        //

 

        //arr3의 각 호실이 콘솔창에 뜨도록하기

        

        //1. for문으로 하기

        for(i=0; i<arr3.length; i++){

            for(z=0; z<arr3[i].length; z++){

                console.log(arr3[i][z]);

            }

        }

 

        //2. for each 문으로 하기

        arr3.forEach (v=>{

            v.forEach (v2=>{

                console.log(v2);

                console.log(k2);

            });

        });

 

 

     </script>