Den här sidan lär dig hur du hittar och kommer åt HTML-element i en HTML-sida.
Ofta, med JavaScript, vill du manipulera HTML-element.
För att göra det måste du hitta elementen först. Det finns flera sätt att göra detta:
Hitta HTML-element efter id
Hitta HTML-element efter taggnamn
Hitta HTML-element efter klassnamn
Hitta HTML-element med CSS-väljare
Hitta HTML-element med HTML-objektsamlingar
Det enklaste sättet att hitta ett HTML-element i DOM är att använda elementet id.
Det här exemplet hittar elementet med id="intro"
:
const element = document.getElementById("intro");
Prova själv →
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript HTML DOM</h2>
<p id="intro">Finding HTML Elements by Id</p>
<p>This example demonstrates the <b>getElementsById</b> method.</p>
<p id="demo"></p>
<script>
const element = document.getElementById("intro");
document.getElementById("demo").innerHTML =
"The text from the intro paragraph is: " + element.innerHTML;
</script>
</body>
</html>
Om elementet hittas kommer metoden att returnera elementet som ett objekt (i element).
Om elementet inte hittas kommer elementet att innehålla null
.
Det här exemplet hittar alla ><p>
-element:
const element = document.getElementsByTagName("p");
Prova själv →
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript HTML DOM</h2>
<p>Finding HTML Elements by Tag Name.</p>
<p>This example demonstrates the <b>getElementsByTagName</b> method.</p>
<p id="demo"></p>
<script>
const element = document.getElementsByTagName("p");
document.getElementById("demo").innerHTML = 'The text in first paragraph (index 0) is: ' + element[0].innerHTML;
</script>
</body>
</html>
Det här exemplet hittar elementet med id="main"
och hittar sedan alla <p>
-element inuti "main"
:
const x = document.getElementById("main");
const y = x.getElementsByTagName("p");
Prova själv →
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript HTML DOM</h2>
<div id="main">
<p>Finding HTML Elements by Tag Name</p>
<p>This example demonstrates the <b>getElementsByTagName</b> method.</p>
</div>
<p id="demo"></p>
<script>
const x = document.getElementById("main");
const y = x.getElementsByTagName("p");
document.getElementById("demo").innerHTML =
'The first paragraph (index 0) inside "main" is: ' + y[0].innerHTML;
</script>
</body>
</html>
Om du vill hitta alla HTML-element med samma klassnamn, använd getElementsByClassName()
.
Det här exemplet returnerar en lista över alla element med class="intro"
.
const x = document.getElementsByClassName("intro");
Prova själv →
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript HTML DOM</h2>
<p>Finding HTML Elements by Class Name.</p>
<p class="intro">Hello World!</p>
<p class="intro">This example demonstrates the <b>getElementsByClassName</b> method.</p>
<p id="demo"></p>
<script>
const x = document.getElementsByClassName("intro");
document.getElementById("demo").innerHTML =
'The first paragraph (index 0) with class="intro" is: ' + x[0].innerHTML;
</script>
</body>
</html>
Om du vill hitta alla HTML-element som matchar en angiven CSS-väljare (id, klassnamn, typer, attribut, värden på attribut, etc), använd metoden querySelectorAll()
.
Det här exemplet returnerar en lista över alla <p>
-element med class="intro"
.
const x = document.querySelectorAll("p.intro");
Prova själv →
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript HTML DOM</h2>
<p>Finding HTML Elements by Query Selector</p>
<p class="intro">Hello World!.</p>
<p class="intro">This example demonstrates the <b>querySelectorAll</b> method.</p>
<p id="demo"></p>
<script>
const x = document.querySelectorAll("p.intro");
document.getElementById("demo").innerHTML =
'The first paragraph (index 0) with class="intro" is: ' + x[0].innerHTML;
</script>
</body>
</html>
Det här exemplet hittar formulärelementet med id="frm1"
, i formulären samling och visar alla element värden:
const x = document.forms["frm1"];
let text = "";
for (let i = 0; i < x.length; i++) {
text += x.elements[i].value + "<br>";
}
document.getElementById("demo").innerHTML = text;
Prova själv →
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript HTML DOM</h2>
<p>Finding HTML Elements Using <b>document.forms</b>.</p>
<form id="frm1" action="/action_page.php">
First name: <input type="text" name="fname" value="Donald"><br>
Last name: <input type="text" name="lname" value="Duck"><br><br>
<input type="submit" value="Submit">
</form>
<p>These are the values of each element in the form:</p>
<p id="demo"></p>
<script>
const x = document.forms["frm1"];
let text = "";
for (let i = 0; i < x.length ;i++) {
text += x.elements[i].value + "<br>";
}
document.getElementById("demo").innerHTML = text;
</script>
</body>
</html>
Följande HTML-objekt (och objektsamlingar) är också tillgängliga:
dokument.ankare
<!DOCTYPE html>
<html>
<body>
<h2>Finding HTML Elements Using document.anchors</h2>
<a name="html">HTML Tutorial</a><br>
<a name="css">CSS Tutorial</a><br>
<a name="xml">XML Tutorial</a><br>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML =
"Number of anchors are: " + document.anchors.length;
</script>
</body>
</html>
document.body
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript HTMLDOM</h2>
<p>Displaying document.body</p>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML = document.body.innerHTML;
</script>
</body>
</html>
document.documentElement
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript HTMLDOM</h2>
<p>Displaying document.documentElement</p>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML = document.documentElement.innerHTML;
</script>
</body>
</html>
document.inbäddar
<!DOCTYPE html>
<html>
<body>
<h2>JavaScript HTMLDOM</h2>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML =
"Number of embeds: " + document.embeds.length;
</script>
</body>
</html>
dokument.formulär
<!DOCTYPE html>
<html>
<body>
<h2>Finding HTML Elements Using document.forms</h2>
<form action="">
First name: <input type="text" name="fname" value="Donald">
<input type="submit" value="Submit">
</form>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML =
"Number of forms: " + document.forms.length;
</script>
</body>
</html>
document.head
<!DOCTYPE html>
<html>
<head>
<title>W3Schools Demo</title>
</head>
<body>
<h2>JavaScript HTMLDOM</h2>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML =
document.head;
</script>
</body>
</html>
dokument.bilder
<!DOCTYPE html>
<html>
<body>
<h2>Finding HTML Elements Using document.images</h2>
<img src="pic_htmltree.gif" width="486" height="266">
<img src="pic_navigate.gif" width="362" height="255">
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML =
"Number of images: " + document.images.length;
</script>
</body>
</html>
document.links
<!DOCTYPE html>
<html>
<body>
<h2>Finding HTML Elements Using document.links</h2>
<p>
<a href="/html/default.asp">HTML</a>
<br>
<a href="/css/default.asp">CSS</a>
</p>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML =
"Number of links: " + document.links.length;
</script>
</body>
</html>
document.scripts
<!DOCTYPE html>
<html>
<body>
<h2>Finding HTML Elements Using document.scripts</h2>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML =
"Number of scripts: " + document.scripts.length;
</script>
</body>
</html>
dokument titel
<!DOCTYPE html>
<html>
<head>
<title>W3Schools Demo</title>
</head>
<body>
<h2>Finding HTML Elements Using document.title</h2>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML =
"The title of this document is: " + document.title;
</script>
</body>
</html>