In CSS, selectors are patterns used to select the element(s) you want to style, but as you can tell from the title above, selectors are also useful in javascript and below are some examples on how to use them.
Basics
Using a selector in javascript
- Use the
.querySelector
method
const div = document.querySelector("div") // => First occurence of a div element in the document
const p = div.querySelector("p") // => First occurence of a p element in the div
- To get all matching elements, use the
document.querySelectorAll
method
document.querySelectorAll("div") // NodeList of all div elements
By IDs
To get an element by its ID, use a #
before the element ID
document.querySelector("#id") // => document.getElementById('id')
By classes
To get elements by class, use a .
before the class name
document.querySelectorAll(".myElementClass")
By tag name
To get elements by tag name, just input the tag name
document.querySelectorAll("body") // => document.getElementsByTagName('body')
Replicating .getElementById
and getElementsByTagName
- Replicating
.getElementById
document.querySelector("#myDivId") // => document.getElementById('myDivId')
- Replicating
.getElementsByTagName
document.querySelectorAll("a") // => document.getElementsByTagName('a')
All elements
To get all elements use *
document.querySelectorAll("*") // => NodeList[...]
Using multiple selectors
To use multiple selectors, we seperate each of them with a ,
.
<html>
<body>
<p>Hello i am a paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<a href="https://anotherplace.com">I am another link</a>
</body>
</html>
document.querySelectorAll("p, a") // => NodeList[p,a,a]
More with elements
In the above examples, we made basic queries, but other things can be done like getting elements by order or parent.
Getting element children
There are two variants of this, one gets an element's child no matter how deep it is down the tree, and the other gets an element's direct child.
<html>
<body>
<p>Hello i am a paragraph</p>
<div>
<a href="https://awesomeplace.com">Hey I am a link</a>
<p>
Hello i am a paragraph and here's
<a href="https://anotherplace.com">a link</a>
</p>
</div>
</body>
</html>
With the above HTML as an example, we will look at these two variants.
- Direct child
document.querySelector("div > a") // => <a href="https://awesomeplace.com">Hey I am a link</a>
- All children
document.querySelectorAll("div a") // => NodeList[a,a]
Getting elements by order
There are two ways to do this also. Consider the following HTML.
<html>
<body>
<div>
<a href="https://awesomeplace.com">Hey I am a link</a>
<pre>I should intervene but i wont</pre>
<p>Hello i am another paragraph</p>
</div>
<p>Hello i am a paragraph</p>
</body>
</html>
- Placed after
document.querySelector("div + p") // => <p>Hello i am a paragraph</p>
- Preceded by
With ~
, it does not matter the element immediately behind matches.
document.querySelector("a ~ p") // => <p>Hello i am another paragraph</p>
and we can see that the pre
element did not affect the result because it does not matter if the pre
was there in the first place. But the following selector will fail because it checks the element immediately above it.
document.querySelector("a + p") // => null
Getting elements by attribute
An attribute selector starts with [
and ends with ]
and is used as such
<html>
<body>
<p style="color:blue;">Hello i am styled</p>
<p>Hello i have no style</p>
</body>
</html>
document.querySelector("p[style]") // => <p style="color:blue;">Hello i am styled</p>
Check attribute value
To check an attribute value we use the =
symbol.
<html>
<body>
<a href="https://awesomeplace.com">Hey I am a link</a>
<a href="https://anotherplace.com">I am another link</a>
</body>
</html>
document.querySelector('a[href="https://awesomeplace.com"]') // => <a href="https://awesomeplace.com">Hey I am a link</a>
More with attribute values
- Check if attribute starts with...
document.querySelector('a[href^="https://awesome"]') // => <a href="https://awesomeplace.com">Hey I am a link</a>
- Check if attribute ends with...
document.querySelectorAll('a[href$=".com"]') // => NodeList[a,a]
- Check if the attribute contains a substring
document.querySelectorAll('a[href*="place"]') // => NodeList[a,a]
Advanced selectors
- :focus
This selects the element that currently has focus
- :visited
This is used with a
tags and selects links that have been visited
- :link
This is also used with a
tags but in this case, selects links that have not been visited
- :enabled
This selects elements that are enabled(not disabled)
<html>
<body>
<p>I am a paragraph</p>
<p>I am another paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<a href="https://anotherplace.com">I am another link</a>
<button disabled="true"> I have been disabled </button>
</body>
</html>
document.querySelectorAll(":enabled") // => NodeList[p,p,a,a]
- :disabled
This selects elements that have been disabled
<html>
<body>
<p>I am a paragraph</p>
<p>I am another paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<a href="https://anotherplace.com">I am another link</a>
<button disabled="true"> I have been disabled </button>
</body>
</html>
document.querySelector(":disabled") // => <button disabled="true"> I have been disabled </button>
- :first-child
This selects the element that is the first child of its parent
<html>
<body>
<p>I am a paragraph</p>
<p>I am another paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<a href="https://anotherplace.com">I am another link</a>
</body>
</html>
document.querySelector("p:first-child") // => <p>I am a paragraph</p>
- :last-child
This selects the element that is the last child of its parent
<html>
<body>
<p>I am a paragraph</p>
<p>I am another paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<a href="https://anotherplace.com">I am another link</a>
</body>
</html>
document.querySelector("p:last-child") // => <a href="anotherplace.com">I am another link</a>
- el:first-of-type
This selects the element that is the first child of its parent and is the same type as el
<html>
<body>
<p>I am a paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<p>I am another paragraph</p>
<a href="https://anotherplace.com">I am another link</a>
</body>
</html>
document.querySelector("a:first-of-type") // => <a href="https://awesomeplace.com">Hey I am a link</a>
- el:last-of-type
This selects the element that is the last child of its parent and is the same type as el
<html>
<body>
<p>I am a paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<p>I am another paragraph</p>
<a href="https://anotherplace.com">I am another link</a>
</body>
</html>
document.querySelector("p:last-of-type") // => <p>I am another paragraph</p>
- :not(selector)
This selects elements that don't match the selector
<html>
<body>
<p>I am a paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<a href="https://anotherplace.com">I am another link</a>
</body>
</html>
document.querySelector(":not(a)") // => <p>I am a paragraph</p>
- :nth-child(n)
This selects the element that is the n th child of its parent.
<html>
<body>
<div>
<p>I am a paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<a href="https://anotherplace.com">I am another link</a>
</div>
</body>
</html>
document.querySelector("div:nth-child(2)") // => <a href="https://awesomeplace.com">Hey I am a link</a>
- :nth-last-child(n)
This selects the element that is the n th to the last child of its parent.
<html>
<body>
<div>
<p>I am a paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<a href="https://anotherplace.com">I am another link</a>
</div>
</body>
</html>
document.querySelector("div:nth-last-child(1)") // => <a href="https://anotherplace.com">I am another link</a>
Mix and match
These selectors can be mixed together to perform some complex checks. e.g
- A disabled button of class 'btn'
<html>
<body>
<div>
<p>I am a paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<a href="https://anotherplace.com">I am another link</a>
</div>
<button disabled="true">I am disabled</button>
<button disabled="true" class="btn">I am also disabled</button>
</body>
</html>
document.querySelector('button.btn:disabled') // => <button disabled="true" class="btn">I am also disabled</button>
- All disabled buttons in a
form
<html>
<body>
<form method="POST">
<input type="text" name="firstname" placeholder="firstname"/>
<input type="text" name="lastname" placeholder="lastname"/>
<button disabled="true">Clear inputs</button>
<button type="submit">Submit</button>
</form>
<button disabled="true">I am disabled</button>
<button disabled="true" class="btn">I am also disabled</button>
</body>
</html>
document.querySelector('form > button:disabled') // => <button disabled="true">Clear inputs</button>
- All disabled buttons in a
form
and all buttons outside it
<html>
<body>
<form method="POST">
<input type="text" name="firstname" placeholder="firstname"/>
<input type="text" name="lastname" placeholder="lastname"/>
<button disabled="true">Clear inputs</button>
<button type="submit">Submit</button>
</form>
<button>I am not disabled</button>
<button class="btn">I am also not disabled</button>
</body>
</html>
document.querySelectorAll('form > button:disabled, form ~ button') // => NodeList[button, button, button]
- All links to external pages
<html>
<body>
<div>
<p>I am a paragraph</p>
<a href="https://awesomeplace.com">Hey I am a link</a>
<a href="https://anotherplace.com">I am another link</a>
</div>
<a href="/otherpage.html">I will to the other pages</a>
</body>
</html>
document.querySelectorAll('a[href^="https://"]') // => NodeList[a,a]
And to get links that are not to external pages, use
document.querySelector('a:not([href^="https://"])') // => <a href="/otherpage.html">I will to the other pages</a>
Conclusion
These are just some of the ways you can use selectors in javascript and if you want to know more, here is a link to a CSS selector reference on w3c.
Top comments (5)
Awesome! I'm using jQuery and several friends told me I should try with pure JavaScript. Looks like the transition will be pretty easy!
This website is helpful if you don't want to use jQuery or want to learn plain javascript.
youmightnotneedjquery.com/
Yeah, since I learned this I haven't been heavily reliant on jQuery 😁
Awesome post. It goes well with this article "The 30 CSS Selectors You Must Memorize"
code.tutsplus.com/tutorials/the-30...
Thank you so much. Now I understood better which I didn’t understand parts. 🙏🏻👏