DOM Changing elements

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Revision as of 17:59, 7 September 2021 by Andr3w (talk | contribs) (→‎Remove France)
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 <div id='countries'> 
  <div id='fr'>
	<div>France</div>
	<img src='/flags/fr.gif'/>
  </div>
  <div id='fi'>
	<div>Finland</div>
	<img src='/flags/fi.gif'/>
  </div>
 </div>

In these examples the web page contains the following content.

<div id='countries'> 
 <div id='fr'>
   <div>France</div>
   <img src='/flags/fr.gif'/>
 </div>
 <div id='fi'>
   <div>Finland</div>
   <img src='/flags/fi.gif'/>
 </div>
</div>

Change an element based on id

If the element you want to change has an id you can use getElementById

  • The html above has a div with id "countries"
Change the countries div to have silver background color.
let e = document.getElementById('countries');
e.style.backgroundColor = 'pink';
let e = document.getElementById('countries');
e.style.backgroundColor = 'silver';

Find an element and change it

You can use document.querySelector to find elements. The pattern given is very like the patterns you use in CSS.

  • 'img' will match a <img/> element
  • '#fr' will match an element with id fr
Make the width of the first img 50px
document.querySelector('img').style.width = '75px';
document.querySelector('img').style.width = '50px';

Find many elements, change them all

You can use document.querySelectorAll to lots of elements.

  • You can visit every element in the list with forEach
Make the width of all img 50px
document.querySelector('img').style.width = '75px';
document.querySelectorAll('img').forEach(i=>{
  i.style.width = '50px';
});

Remove France

The element with id fr must go.

Use .remove() to remove France

document.querySelector('#fr').remove();

Swap the order

You can use append to reinsert an element.

  • You must find the list of countries
  • You must find the target country
  • You must append the target to the list
Use .append() to put France at the end

document.getElementById('countries')
  .append(document.getElementById('fr'));