Conditionally Rendering Elements with v-if
Hello, students! Welcome to Lesson 3 of Vue.js Directives. Today, we will learn about the v-if
directive and how to use it to conditionally render elements.
What is the v-if Directive?
The v-if
directive allows you to conditionally render an element. It is one of the most powerful directives in Vue.js.
How to Use the v-if Directive?
The basic syntax of the v-if
directive is as follows:
<element v-if="condition">
Where:
element
is the element you want to conditionally render.condition
is a JavaScript expression that determines whether the element will be rendered.
Example
Let’s see an example of how to use the v-if
directive to render an element only if the user is logged in:
<div v-if="isLoggedIn"> <h1>Hello, user!</h1> </div>
In the above example, the div
element will be rendered only if the isLoggedIn
property is true.
Other Examples
Let’s see some other examples of how to use the v-if
directive:
- Rendering an element only if the value of a property is greater than a certain value:
<div v-if="age > 18"> <h1>You are of legal age.</h1> </div>
- Rendering an element only if the user selects an option from a menu:
<div v-if="option === 'option 1'"> <h1>You selected option 1.</h1> </div>
JavaScript Expressions in the v-if Directive
You can use JavaScript expressions in the v-if
directive to determine whether the element will be rendered.
For example, let’s see an example of how to use the v-if
directive to render an element only if the current time value is greater than 12:
<div v-if="new Date().getHours() > 12">
<h1>Good afternoon!</h1>
</div>
In the above example, the div
element will be rendered only if the current time value is greater than 12.
Challenge
Here’s a challenge for you:
- Create a Vue.js application that displays the user’s name only if they are logged in.
Good luck!
Tip
You can use the v-if
directive to create a form that only allows the user to submit the form if all required fields are filled.