DOM

	<select name="셀렉태그" id="sel">
        <option value="1">셀렉 옵션1</option>
        <option value="2">셀렉 옵션2</option>
        <option value="3">셀렉 옵션3</option>
        <option value="4">셀렉 옵션4</option>
    </select>

	<label for="">체크박스1 <input type="checkbox" value="1" class="check1"></label>
    <label for="">체크박스2 <input type="checkbox" value="2" class="check2"></label>
    <label for="">체크박스3 <input type="checkbox" value="3" class="check3"></label>

    <script>
        let 셀렉 = document.querySelector("select")
        console.log(셀렉.options)
        console.log(셀렉.options[0]) // 첫번째 option태그 확인
        console.log(셀렉.options[0].value)
        console.log(셀렉.options[0].innerHTML)
        console.log(셀렉.options[0].textContent)
        셀렉.options[0].textContent = "수정한 셀렉"
    </script>

    <script>
        셀렉.addEventListener("change", () => {
            console.log(셀렉.options.selectedIndex)
        })
    </script>

    <script>
        let 체크박스1 = document.querySelector(".check1")
        체크박스1.addEventListener("change", () => {
            console.log(체크박스1.checked)
            console.log(체크박스1.value)
            console.log(체크박스1.id) // 있으면 출력됨
            console.log(체크박스1.name) // 있으면 출력됨
            
        })
    </script>

반복문

1부터 100까지 1간격으로 출력

	<script>
        for (let i = 1; i <= 100; i = i + 1) {
        	console.log(i)
        }
    </script>

1부터 10까지의 숫자의 합

	<script>
        let sum = 0
        for (let i = 1; i <= 10; i += 1) {
            sum += i
        }
        console.log(sum)
    </script>