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freeCodeCamp/curriculum/challenges/english/03-front-end-development-libraries/react/use-a-ternary-expression-for-conditional-rendering.md
Shaun Hamilton c2a11ad00d feat: add 'back/front end' in curriculum (#42596)
* chore: rename APIs and Microservices to include "Backend" (#42515)

* fix typo

* fix typo

* undo change

* Corrected grammar mistake

Corrected a grammar mistake by removing a comma.

* change APIs and Microservices cert title

* update title

* Change APIs and Microservices certi title

* Update translations.json

* update title

* feat(curriculum): rename apis and microservices cert

* rename folder structure

* rename certificate

* rename learn Markdown

* apis-and-microservices -> back-end-development-and-apis

* update backend meta

* update i18n langs and cypress test

Co-authored-by: Shaun Hamilton <shauhami020@gmail.com>

* fix: add development to front-end libraries (#42512)

* fix: added-the-word-Development-to-front-end-libraries

* fix/added-the-word-Development-to-front-end-libraries

* fix/added-word-development-to-front-end-libraries-in-other-related-files

* fix/added-the-word-Development-to-front-end-and-all-related-files

* fix/removed-typos-from-last-commit-in-index.md

* fix/reverted-changes-that-i-made-to-dependecies

* fix/removed xvfg

* fix/reverted changes that i made to package.json

* remove unwanted changes

* front-end-development-libraries changes

* rename backend certSlug and README

* update i18n folder names and keys

* test: add legacy path redirect tests

This uses serve.json from the client-config repo, since we currently use
that in production

* fix: create public dir before moving serve.json

* fix: add missing script

* refactor: collect redirect tests

* test: convert to cy.location for stricter tests

* rename certificate folder to 00-certificates

* change crowdin config to recognise new certificates location

* allow translations to be used

Co-authored-by: Nicholas Carrigan (he/him) <nhcarrigan@gmail.com>

* add forwards slashes to path redirects

* fix cypress path tests again

* plese cypress

* fix: test different challenge

Okay so I literally have no idea why this one particular challenge
fails in Cypress Firefox ONLY. Tom and I paired and spun a full build
instance and confirmed in Firefox the page loads and redirects as
expected. Changing to another bootstrap challenge passes Cypress firefox
locally. Absolutely boggled by this.

AAAAAAAAAAAAAAA

* fix: separate the test

Okay apparently the test does not work unless we separate it into
a different `it` statement.

>:( >:( >:( >:(

Co-authored-by: Sujal Gupta <55016909+heysujal@users.noreply.github.com>
Co-authored-by: Noor Fakhry <65724923+NoorFakhry@users.noreply.github.com>
Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>
Co-authored-by: Nicholas Carrigan (he/him) <nhcarrigan@gmail.com>
2021-08-13 21:57:13 -05:00

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---
id: 5a24c314108439a4d4036187
title: Use a Ternary Expression for Conditional Rendering
challengeType: 6
forumTopicId: 301414
dashedName: use-a-ternary-expression-for-conditional-rendering
---
# --description--
Before moving on to dynamic rendering techniques, there's one last way to use built-in JavaScript conditionals to render what you want: the <dfn>ternary operator</dfn>. The ternary operator is often utilized as a shortcut for `if/else` statements in JavaScript. They're not quite as robust as traditional `if/else` statements, but they are very popular among React developers. One reason for this is because of how JSX is compiled, `if/else` statements can't be inserted directly into JSX code. You might have noticed this a couple challenges ago — when an `if/else` statement was required, it was always *outside* the `return` statement. Ternary expressions can be an excellent alternative if you want to implement conditional logic within your JSX. Recall that a ternary operator has three parts, but you can combine several ternary expressions together. Here's the basic syntax:
```jsx
condition ? expressionIfTrue : expressionIfFalse;
```
# --instructions--
The code editor has three constants defined within the `CheckUserAge` component's `render()` method. They are called `buttonOne`, `buttonTwo`, and `buttonThree`. Each of these is assigned a simple JSX expression representing a button element. First, initialize the state of `CheckUserAge` with `input` and `userAge` both set to values of an empty string.
Once the component is rendering information to the page, users should have a way to interact with it. Within the component's `return` statement, set up a ternary expression that implements the following logic: when the page first loads, render the submit button, `buttonOne`, to the page. Then, when a user enters their age and clicks the button, render a different button based on the age. If a user enters a number less than `18`, render `buttonThree`. If a user enters a number greater than or equal to `18`, render `buttonTwo`.
# --hints--
The `CheckUserAge` component should render with a single `input` element and a single `button` element.
```js
assert(
Enzyme.mount(React.createElement(CheckUserAge)).find('div').find('input')
.length === 1 &&
Enzyme.mount(React.createElement(CheckUserAge)).find('div').find('button')
.length === 1
);
```
The `CheckUserAge` component's state should be initialized with a property of `userAge` and a property of `input`, both set to a value of an empty string.
```js
assert(
Enzyme.mount(React.createElement(CheckUserAge)).state().input === '' &&
Enzyme.mount(React.createElement(CheckUserAge)).state().userAge === ''
);
```
When the `CheckUserAge` component is first rendered to the DOM, the `button`'s inner text should be Submit.
```js
assert(
Enzyme.mount(React.createElement(CheckUserAge)).find('button').text() ===
'Submit'
);
```
When a number of less than 18 is entered into the `input` element and the `button` is clicked, the `button`'s inner text should read `You Shall Not Pass`.
```js
(() => {
const mockedComponent = Enzyme.mount(React.createElement(CheckUserAge));
const initialButton = mockedComponent.find('button').text();
const enter3AndClickButton = () => {
mockedComponent
.find('input')
.simulate('change', { target: { value: '3' } });
mockedComponent.find('button').simulate('click');
mockedComponent.update();
return mockedComponent.find('button').text();
};
const enter17AndClickButton = () => {
mockedComponent
.find('input')
.simulate('change', { target: { value: '17' } });
mockedComponent.find('button').simulate('click');
mockedComponent.update();
return mockedComponent.find('button').text();
};
const userAge3 = enter3AndClickButton();
const userAge17 = enter17AndClickButton();
assert(
initialButton === 'Submit' &&
userAge3 === 'You Shall Not Pass' &&
userAge17 === 'You Shall Not Pass'
);
})();
```
When a number greater than or equal to 18 is entered into the `input` element and the `button` is clicked, the `button`'s inner text should read `You May Enter`.
```js
(() => {
const mockedComponent = Enzyme.mount(React.createElement(CheckUserAge));
const initialButton = mockedComponent.find('button').text();
const enter18AndClickButton = () => {
mockedComponent
.find('input')
.simulate('change', { target: { value: '18' } });
mockedComponent.find('button').simulate('click');
mockedComponent.update();
return mockedComponent.find('button').text();
};
const enter35AndClickButton = () => {
mockedComponent
.find('input')
.simulate('change', { target: { value: '35' } });
mockedComponent.find('button').simulate('click');
mockedComponent.update();
return mockedComponent.find('button').text();
};
const userAge18 = enter18AndClickButton();
const userAge35 = enter35AndClickButton();
assert(
initialButton === 'Submit' &&
userAge18 === 'You May Enter' &&
userAge35 === 'You May Enter'
);
})();
```
Once a number has been submitted, and the value of the `input` is once again changed, the `button` should return to reading `Submit`.
```js
(() => {
const mockedComponent = Enzyme.mount(React.createElement(CheckUserAge));
const enter18AndClickButton = () => {
mockedComponent
.find('input')
.simulate('change', { target: { value: '18' } });
mockedComponent.find('button').simulate('click');
mockedComponent.update();
return mockedComponent.find('button').text();
};
const changeInputDontClickButton = () => {
mockedComponent
.find('input')
.simulate('change', { target: { value: '5' } });
mockedComponent.update();
return mockedComponent.find('button').text();
};
const enter10AndClickButton = () => {
mockedComponent
.find('input')
.simulate('change', { target: { value: '10' } });
mockedComponent.find('button').simulate('click');
mockedComponent.update();
return mockedComponent.find('button').text();
};
const userAge18 = enter18AndClickButton();
const changeInput1 = changeInputDontClickButton();
const userAge10 = enter10AndClickButton();
const changeInput2 = changeInputDontClickButton();
assert(
userAge18 === 'You May Enter' &&
changeInput1 === 'Submit' &&
userAge10 === 'You Shall Not Pass' &&
changeInput2 === 'Submit'
);
})();
```
Your code should not contain any `if/else` statements.
```js
assert(
new RegExp(/(\s|;)if(\s|\()/).test(
Enzyme.mount(React.createElement(CheckUserAge)).instance().render.toString()
) === false
);
```
# --seed--
## --after-user-code--
```jsx
ReactDOM.render(<CheckUserAge />, document.getElementById('root'));
```
## --seed-contents--
```jsx
const inputStyle = {
width: 235,
margin: 5
};
class CheckUserAge extends React.Component {
constructor(props) {
super(props);
// Change code below this line
// Change code above this line
this.submit = this.submit.bind(this);
this.handleChange = this.handleChange.bind(this);
}
handleChange(e) {
this.setState({
input: e.target.value,
userAge: ''
});
}
submit() {
this.setState(state => ({
userAge: state.input
}));
}
render() {
const buttonOne = <button onClick={this.submit}>Submit</button>;
const buttonTwo = <button>You May Enter</button>;
const buttonThree = <button>You Shall Not Pass</button>;
return (
<div>
<h3>Enter Your Age to Continue</h3>
<input
style={inputStyle}
type='number'
value={this.state.input}
onChange={this.handleChange}
/>
<br />
{/* Change code below this line */}
{/* Change code above this line */}
</div>
);
}
}
```
# --solutions--
```jsx
const inputStyle = {
width: 235,
margin: 5
};
class CheckUserAge extends React.Component {
constructor(props) {
super(props);
this.state = {
userAge: '',
input: ''
};
this.submit = this.submit.bind(this);
this.handleChange = this.handleChange.bind(this);
}
handleChange(e) {
this.setState({
input: e.target.value,
userAge: ''
});
}
submit() {
this.setState(state => ({
userAge: state.input
}));
}
render() {
const buttonOne = <button onClick={this.submit}>Submit</button>;
const buttonTwo = <button>You May Enter</button>;
const buttonThree = <button>You Shall Not Pass</button>;
return (
<div>
<h3>Enter Your Age to Continue</h3>
<input
style={inputStyle}
type='number'
value={this.state.input}
onChange={this.handleChange}
/>
<br />
{this.state.userAge === ''
? buttonOne
: this.state.userAge >= 18
? buttonTwo
: buttonThree}
</div>
);
}
}
```