Vue v-if
Directive
It is a lot easier to create an HTML element depending on a condition in Vue with the v-if
directive than with plain JavaScript.
With Vue you just write the if-statement directly in the HTML element you want to create conditionally. It's that simple.
Conditional Rendering in Vue
Conditional rendering in Vue is done by using the v-if
, v-else-if
and v-else
directives.
Conditional rendering is when an HTML element is created only if a condition is true, i.e. create the text "In stock" if a variable is 'true', or 'Not in stock' if that variable is 'false'.
ExampleGet your own Vue Server
Write different messages depending on whether there are any typewriters in stock or not:
<p v-if="typewritersInStock">
in stock
</p>
<p v-else>
not in stock
</p>
Try it Yourself »
Conditions in Vue
A condition, or "if-statement", is something that is either true
or false
.
A condition is often a comparison check between two values like in the example above to see if one value is greater than the other.
We use comparison operators like
<
,>=
or!==
to do such checks.Comparison checks can also be combined with logical operators such as
&&
or||
.Go to our JavaScript tutorial page to find out more about JavaScript comparisons.
We can use the number of typewriters in storage with a comparison check to decide if they are in stock or not:
Example
Use a comparison check to decide whether to write "In stock" or "Not in stock" depending on the number of typewriters in storage.
<p v-if="typewriterCount > 0">
in stock
</p>
<p v-else>
not in stock
</p>
Try it Yourself »
Directives for Conditional Rendering
This overview describes how the different Vue directives used for conditional rendering are used together.
Directive | Details |
---|---|
v-if |
Can be used alone, or with v-else-if and/or v-else . If the condition inside v-if is 'true', v-else-if or v-else are not considered. |
v-else-if |
Must be used after v-if or another v-else-if . If the condition inside v-else-if is 'true', v-else-if or v-else that comes after are not considered. |
v-else |
This part will happen if the first part of the if-statement is false. Must be placed at the very end of the if-statement, after v-if and v-else-if . |
To see an example with all three directives shown above, we can expand the previous example with v-else-if
so that the user sees 'In stock', 'Very few left!' or 'Out of stock':
Example
Use a comparison check to decide whether to write "In stock", "Very few left!" or "Not in stock" depending on the number of typewriters in storage.
<p v-if="typewriterCount>3">
In stock
</p>
<p v-else-if="typewriterCount>0">
Very few left!
</p>
<p v-else>
Not in stock
</p>
Try it Yourself »
Use The Return Value from a Function
Instead of using a comparison check with the v-if
directive, we can use the 'true' or 'false' return value from a function:
Example
If a certain text contains the word 'pizza', create a <p> tag with an appropriate message. The 'includes()' method is a native JavaScript method that checks if a text contain certain words.
<div id="app">
<p v-if="text.includes('pizza')">The text includes the word 'pizza'</p>
<p v-else>The word 'pizza' is not found in the text</p>
</div>
data() {
return {
text: 'I like taco, pizza, Thai beef salad, pho soup and tagine.'
}
}
Try it Yourself »
The example above can be expanded to show that v-if
also can create other tags like <div> and <img> tags:
Example
If a certain text contains the word 'pizza', create a <div> tag with a pizza image and a <p> tag with a message. The 'includes()' method is a native JavaScript method that check if a text contain certain words.
<div id="app">
<div v-if="text.includes('pizza')">
<p>The text includes the word 'pizza'</p>
<img src="img_pizza.svg">
</div>
<p v-else>The word 'pizza' is not found in the text</p>
</div>
<script src="https://unpkg.com/vue@3/dist/vue.global.js"></script>
<script>
const app = Vue.createApp({
data() {
return {
text: 'I like taco, pizza, Thai beef salad, pho soup and tagine.'
}
}
})
app.mount('#app')
</script>
Try it Yourself »
Below the example is expanded even more.
Example
If a certain text contains the word 'pizza' or 'burrito' or none of these words, different images and texts will be created.
<div id="app">
<div v-if="text.includes('pizza')">
<p>The text includes the word 'pizza'</p>
<img src="img_pizza.svg">
</div>
<div v-else-if="text.includes('burrito')">
<p>The text includes the word 'burrito', but not 'pizza'</p>
<img src="img_burrito.svg">
</div>
<p v-else>The words 'pizza' or 'burrito' are not found in the text</p>
</div>
<script src="https://unpkg.com/vue@3/dist/vue.global.js"></script>
<script>
const app = Vue.createApp({
data() {
return {
text: 'I like taco, pizza, Thai beef salad, pho soup and tagine.'
}
}
})
app.mount('#app')
</script>
Try it Yourself »
With Vue we can now write code that create elements under certain conditions in a much easier way than with traditional JavaScript.