JSX in Vue components

Introduction

JSX lets you write HTML-like code inside JavaScript. In Vue, it helps you build components using JavaScript syntax instead of templates.

You want to use JavaScript logic directly inside your component's render output.

You prefer writing UI with JavaScript instead of Vue's template syntax.

You need to create dynamic elements or lists with complex conditions.

You want to reuse UI pieces as JavaScript functions easily.

You are integrating Vue with other JavaScript libraries that use JSX.

Syntax

Vue

import { defineComponent } from 'vue';

export default defineComponent({
  setup() {
    return () => (
      <div>Hello JSX in Vue!</div>
    );
  }
});

JSX code goes inside the return () => ( ... ) function in setup().

Use parentheses ( ) to wrap JSX elements for clarity.

Examples

Simple JSX returning a heading element.

Vue

export default {
  setup() {
    return () => <h1>Title with JSX</h1>;
  }
};

JSX with JavaScript expression inside curly braces to show a variable.

Vue

export default {
  setup() {
    const name = 'Vue';
    return () => <p>Hello, {name}!</p>;
  }
};

JSX rendering a list using map() with keys for each item.

Vue

export default {
  setup() {
    const items = ['Apple', 'Banana', 'Cherry'];
    return () => (
      <ul>
        {items.map(item => <li key={item}>{item}</li>)}
      </ul>
    );
  }
};

Sample Program

This Vue component uses JSX to show a count and a button. Clicking the button increases the count. It uses ref for reactive state and onClick for the button event.

The button has an aria-label for accessibility.

Vue

import { defineComponent, ref } from 'vue';

export default defineComponent({
  setup() {
    const count = ref(0);
    const increment = () => {
      count.value++;
    };
    return () => (
      <div>
        <p>Count: {count.value}</p>
        <button onClick={increment} aria-label="Increment count">Add 1</button>
      </div>
    );
  }
});

Important Notes

JSX in Vue requires a build step with tools like Vite or Vue CLI configured to support JSX.

Use onClick (camelCase) for event handlers in JSX, not lowercase onclick.

Always add key props when rendering lists to help Vue track elements efficiently.

Summary

JSX lets you write HTML-like code inside JavaScript functions in Vue components.

It is useful for dynamic UI and when you prefer JavaScript over templates.

Remember to use return () => ( ... ) in setup() and wrap JSX in parentheses.

Practice

1. What is the main purpose of using JSX in Vue components?

easy

A. To write HTML-like code inside JavaScript functions for UI rendering

B. To replace JavaScript with HTML code

C. To write CSS styles directly inside Vue components

D. To create Vue components without any JavaScript

Solution

1. Step 1: Understand JSX role in Vue

   JSX allows writing HTML-like syntax inside JavaScript, making UI code dynamic and easier to manage.

2. Step 2: Compare options

   Only To write HTML-like code inside JavaScript functions for UI rendering correctly describes JSX's purpose. Others confuse JSX with CSS or removing JavaScript.

3. Final Answer:

   To write HTML-like code inside JavaScript functions for UI rendering -> Option A

4. Quick Check:

   JSX = HTML-like code in JS [OK]

Hint: JSX mixes HTML look inside JavaScript functions [OK]

Common Mistakes:

• Thinking JSX replaces JavaScript entirely
• Confusing JSX with CSS styling
• Believing JSX removes the need for Vue components

2. Which of the following is the correct way to return JSX inside the setup() function in Vue 3?

easy

A. return Hello;

B. return function() { Hello };

C. return () => (Hello);

D. return { template: 'Hello' };

Solution

1. Step 1: Recall Vue 3 setup JSX syntax

   In Vue 3, setup() returns a render function, usually an arrow function returning JSX wrapped in parentheses.

2. Step 2: Evaluate options

   return () => (
   Hello); correctly returns an arrow function with JSX. return

   Hello

   ; returns JSX directly (invalid). return function() {

   Hello

   }; returns a function but misses return statement. return { template: '

   Hello

   ' }; uses template string, not JSX.

3. Final Answer:

   return () => (<div>Hello</div>); -> Option C

4. Quick Check:

   setup returns arrow function with JSX [OK]

Hint: Always return an arrow function wrapping JSX in setup() [OK]

Common Mistakes:

• Returning JSX directly without a function
• Using function without return statement
• Confusing JSX with template strings

3. What will be the rendered output of this Vue JSX component?

import { defineComponent } from 'vue';
export default defineComponent({
  setup() {
    const name = 'Vue';
    return () => (
      

        
Hello, {name}!
      
    );
  }
});

medium

A. Hello, Vue!

B. Hello, {name}!

C. Hello, !

D. SyntaxError due to JSX expression

Solution

1. Step 1: Understand JSX expression interpolation

   In JSX, curly braces insert JavaScript expressions. Here, {name} inserts the string 'Vue'.

2. Step 2: Predict rendered HTML

   The component renders a div with an h1 containing 'Hello, Vue!'. No syntax errors occur.

3. Final Answer:

   <div><h1>Hello, Vue!</h1></div> -> Option A

4. Quick Check:

   JSX {name} inserts variable value [OK]

Hint: JSX curly braces insert JavaScript values directly [OK]

Common Mistakes:

• Thinking JSX shows variable name literally
• Expecting empty output if variable used
• Assuming JSX causes syntax errors without Babel

4. Identify the error in this Vue JSX component code:

import { defineComponent } from 'vue';
export default defineComponent({
  setup() {
    const count = 0;
    return () => {
      {count}
    };
  }
});

medium

A. count variable should be reactive

B. JSX cannot be used inside setup()

C. setup() should not return a function

D. Missing parentheses around JSX in return function

Solution

1. Step 1: Check JSX return syntax in arrow function

   The arrow function uses curly braces but does not return JSX explicitly or wrap JSX in parentheses, causing no output.

2. Step 2: Correct syntax for returning JSX

   JSX must be wrapped in parentheses and returned explicitly, e.g., () => ( <button>{count}</button> ).

3. Final Answer:

   Missing parentheses around JSX in return function -> Option D

4. Quick Check:

   JSX must be wrapped in parentheses and returned [OK]

Hint: Wrap JSX in parentheses when returning from arrow function [OK]

Common Mistakes:

• Forgetting to return JSX explicitly
• Not wrapping JSX in parentheses
• Thinking reactive is required for static display

5. You want to create a Vue JSX component that renders a list of items passed as a prop. Which is the correct way to map the items array to JSX elements inside setup()?

hard

A. return () => ({props.items.forEach(item => {item})});

B. return () => ({props.items.map(item => {item})});

C. return () => ({for (const item of props.items) {item}});

D. return () => ({props.items.map(item => '' + item + '')});

Solution

1. Step 1: Understand how to render lists in JSX

   JSX uses JavaScript expressions. map() returns an array of JSX elements, perfect for rendering lists.

2. Step 2: Evaluate each option

   return () => (
   {props.items.map(item =>
   • {item}
   )}
   ); correctly uses map() to return
3. elements. return () => (
   {props.items.forEach(item =>
   • {item}
   )}
   ); uses forEach which returns undefined. return () => (
   {for (const item of props.items)
   • {item}
   }
   ); uses invalid syntax inside JSX. return () => (
   {props.items.map(item => '
   • ' + item + '
   ')}
   ); returns strings, not JSX elements.

4. Final Answer:

   return () => (<ul>{props.items.map(item => <li>{item}</li>)}); -> Option B

5. Quick Check:

   Use map() to return JSX list items [OK]

Hint: Use map() to create JSX elements for lists [OK]

Common Mistakes:

• Using forEach instead of map for JSX lists
• Trying to use for loops inside JSX expressions
• Returning strings instead of JSX elements