documnet Elemnet : <a></a> Attribute : "href" Text : <a>mylink</a> (mylink)2.網頁解析由上而下
<script></script> JS建議放於網頁下面等DOM解析完成使用才不會有問題3.querySelector(選取第一個符合元素)
<h1 class="header">1234</h1>
<script>
const el = document.querySelector('.header');
console.log(el);//<h1 class="header">1234</h1>
</script>
4.元素修改或插入文字
<h1 class="header">1234</h1>
<script>
const el = document.querySelector('.header');
el.textContent = "5678";
console.log(el);
//簡短寫法
document.querySelector('.header').textContent ="01010";
console.log(el); //<h1 class="header">01010</h1>
</script>
5.元素加入HTML標籤(innerHTML刪除內容後再加入)
<main></main>
<script>
const main = document.querySelector('main');
main.innerHTML =`<h1>1234</h1>`;//加入html標籤
const h1 = document.querySelector('h1');
console.log(h1);//<h1>1234</h1>
</script>
6.innerHTML、textContent差異
<main></main>
<script>
const main = document.querySelector('main');
main.innerHTML =`<h1>123</h1>`;//html標籤
main.textContent=`<h1>123</h1>`;//會是文字
</script>
7.setAttribute加入屬性，getAttribute取得屬性，innerHTML取得html，textContent取得文字
<a></a>
<script>
const myLink = document.querySelector('a');
myLink.innerHTML = "<span>Google</sapn>";
//設定Attribute
myLink.setAttribute("href", "https://www.google.com");
myLink.setAttribute("target", "_blank");
//取出設定Attribute
console.log(myLink.getAttribute("href"));//https://www.google.com
console.log(myLink.getAttribute("target"));//_blank
console.log(myLink.innerHTML);//<span>Google</span>
console.log(myLink.textContent);//google
</script>
8.querySelectorAll,回傳NodeList陣列
<a>Google</a>
<a>Yahoo</a>
<script>
const myLinks = document.querySelectorAll('a');//會回傳NodeList陣列
console.log(myLinks);
myLinks[0].setAttribute("href", "https://www.google.com");
myLinks[1].setAttribute("href", "https://tw.yahoo.com");
</script>
9.表單元素取值、賦值
<input type="text" class="txt" value="早安" />
<select class="list">
<option value="1">1</option>
<option value="2">2</option>
</select>
<script>
const txt = document.querySelector('.txt');
console.log(txt.value);//早安
txt.value = "晚安"; //賦值
console.log(txt.value);//晚安
const list = document.querySelector('.list');
console.log(list);//<select class="list"><option value="1">1</option><option value="2">2</option></select>
console.log(list.value);//1
list.value = 2; //賦值
console.log(list.value);//2
</script>
10.addEventListener註冊監聽事件是否有註冊監聽，chrome > F12 > 元素上檢查 > Even Listeners
<ul class="list">
<li><span>hihi</span></li>
<li>hihi <input type="button" value="按鈕" class="btn"></li>
</ul>
<h1></h1>
<script>
const btn = document.querySelector('.list');
//const btn = document.querySelector('.btn');
const h1 = document.querySelector('h1');
let count = 0;
btn.addEventListener('click', function (e) {
if (e.target.nodeName == "INPUT") {
//btn.addEventListener('click', function (e) {
count++;
h1.textContent = `手速測試，您點擊了${count}次`;
} else {
console.log(e);//捕捉當下元素資訊
console.log(e.clientX);
console.log(btn.nodeName);//INPUT 目前的元素tag
console.log(e.target);//偵測到目前點擊是哪個元素
console.log(e.target.nodeName);//INPUT
console.log(e.target.innerHTML);
console.log(e.target.textContent);
h1.textContent = `點到${e.target.nodeName}`;
}
});
</script>
11.preventDefault取消預設觸發行為
<a href="http://tw.yahoo.com">yahoo</a>
<script>
const myLink = document.querySelector('a');
myLink.addEventListener('click', function (e) {
e.preventDefault();
console.log('有點點到,但不會轉址');
});
</script>
參考資料JS直播班 - 上課白板
