JavaScript/Changing elements
On this page, we show how to change two different things of an HTML element, respectively, DOM node.
- Its content (there is only one - or none)
- Any of its attributes (there may be many)
Please take note of this distinction between content and attributes.
<!-- in general: --> <element_name attribute_name="attribute_value">content of the element</element_name> <!-- a concrete example. 'href' is an attribute. 'Visit IANA...' is the content. --> <a href="https://www.example.com">Visit IANA's example domain.</a> Example page
[edit | edit source]We use the following example HTML page to demonstrate the possibilities.
<!DOCTYPE html> <html> <head> <script> function show() { "use strict"; // ... } </script> </head> <body id="body" style="margin:2em"> <p id="p1" style="background: aqua">A blue paragraph</p> <svg id="svgSrc" width="100" height="100" viewBox="0 0 100 100"> <circle cx="50" cy="50" r="25" fill="green"/> </svg> <p /> <a id="refToSomewhere" href="https://www.example.com">Visit IANA's example domain.</a> <p /> <button id="buttonShow" onclick="show()">Start</button> </body> </html> Clicking on the button invokes the function show. The examples should be included there.
Change the content
[edit | edit source]We use the example of a paragraph p. To change its content, the text, just assign the new value to its innerHTML.
function show() { "use strict"; const elem = document.getElementById("p1"); elem.innerHTML = "New text in the paragraph."; } Or, to do the same with a different HTML element, we change the SVG graphic.
function show() { "use strict"; const elem = document.getElementById("svgSrc"); elem.innerHTML = "<rect width='80' height='40' fill='blue'/>"; } Because the new text is HTML code, you can 'misuse' this approach to add child nodes.
function show() { "use strict"; const elem = document.getElementById("p1"); elem.innerHTML = "New text in the paragraph.<p>next P</p><p>and even one more P</p>"; } The script inserts two more paragraphs, but not behind the first one. They are within the first one.
<p id="p1">New text in the paragraph <p>next P</p> <p>and even one more P</p> </p> Change an attribute
[edit | edit source]In general, the syntax to change attributes is as follows:
element_name.attribute_name = "new value"; // or: element_name.setAttribute("attribute_name", "new value"); The HTML element a knows a href attribute: <a id="refToSomewhere" href="https://www.example.com">...</a>. This href attribute can be changed:
function show() { "use strict"; const elem = document.getElementById("refToSomewhere"); elem.href = "https://en.wikibooks.org"; elem.innerHTML = "Link changed"; } First, the element is located. Second, the function assigns a new value to its attribute 'href' (and to the innerHTML).
The following example changes the src attribute of img element and the value attribute of button element
// The HTML <img id="imgOne" src="myPicture.jpg"> <input id="buttonOne" value="I'm a button!"> // The JavaScript document.getElementById("imgOne").src = "otherPicture.jpg"; const b = document.getElementById("buttonOne"); b.value = "I'm a changed button"; setAttribute()
[edit | edit source]The modification of attributes can also be done via the function setAttribute.
function show() { "use strict"; const elem = document.getElementById("refToSomewhere"); elem.setAttribute("href", "https://en.wikibooks.org"); elem.innerHTML = "Link changed"; }