REST API with JavaScript in Wordpress - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a REST API?

A REST API is a way for different programs to talk to each other over the internet using simple commands like GET, POST, PUT, and DELETE. It works like ordering food at a restaurant: you send a request, and you get a response.

beginner

How do you fetch data from a WordPress REST API using JavaScript?

You use the fetch() function with the WordPress REST API URL. For example, fetch('https://example.com/wp-json/wp/v2/posts') gets the list of posts in JSON format.

beginner

What HTTP method do you use to create a new post via the WordPress REST API?

You use the POST method to send new data to the server and create a new post.

intermediate

Why do you need to include authentication when modifying WordPress data via REST API?

Because changing data like creating or deleting posts needs permission. Authentication proves you have the right to make those changes.

beginner

What is the purpose of the 'wp-json' part in the WordPress REST API URL?

The 'wp-json' part tells WordPress to use its REST API system to send or receive data in JSON format.

Which JavaScript function is commonly used to call a REST API?

A fetch()

B alert()

C console.log()

D setTimeout()

fetch() is used to make network requests, including calling REST APIs.

What HTTP method is used to update existing data in a REST API?

A GET

B POST

C PUT

D DELETE

PUT is used to update existing data on the server.

In WordPress REST API, what does the endpoint '/wp-json/wp/v2/posts' return?

A List of pages

B List of posts

C List of comments

D List of users

This endpoint returns the list of posts in WordPress.

Why is authentication important when using REST API to modify WordPress content?

A To avoid using HTTPS

B To speed up the request

C To get data faster

D To prove permission to change data

Authentication proves you have permission to make changes.

Which format does WordPress REST API use to send data?

A JSON

B XML

C CSV

D HTML

WordPress REST API uses JSON format for data exchange.

Explain how you would use JavaScript to get a list of posts from a WordPress site using the REST API.

Think about sending a request and reading the response.

Describe why authentication is necessary when creating or deleting posts via the WordPress REST API.

Consider site security and permissions.

Practice

1. What is the main purpose of using the WordPress REST API with JavaScript?

easy

A. To get or send data to the WordPress server without reloading the page

B. To change the WordPress theme colors

C. To install WordPress plugins automatically

D. To create new WordPress users manually

Solution

1. Step 1: Understand REST API role

   The REST API allows JavaScript to communicate with the server asynchronously.

2. Step 2: Identify the purpose in WordPress context

   It is used to get or send data like posts or pages without reloading the page.

3. Final Answer:

   To get or send data to the WordPress server without reloading the page -> Option A

4. Quick Check:

   REST API = Data exchange without reload [OK]

Hint: REST API means data exchange without page reload [OK]

Common Mistakes:

• Thinking REST API changes themes or plugins
• Confusing REST API with WordPress admin tasks
• Assuming REST API reloads the page

2. Which of the following is the correct way to fetch posts from the WordPress REST API using JavaScript?

easy

A. fetch('/wp-json/wp/v2/posts').then(response => response.json())

B. fetch('wp-json/wp/v2/posts').json()

C. fetch('/wp-json/wp/v2/posts').json()

D. fetch('/wp-json/wp/v2/posts').then(response => response.text())

Solution

1. Step 1: Check fetch URL format

   The URL must start with a slash '/' to indicate root path: '/wp-json/wp/v2/posts'.

2. Step 2: Use correct response method

   Use response.json() inside a then() to parse JSON data correctly.

3. Final Answer:

   fetch('/wp-json/wp/v2/posts').then(response => response.json()) -> Option A

4. Quick Check:

   fetch + .then + response.json() = correct syntax [OK]

Hint: Use .then(response => response.json()) after fetch [OK]

Common Mistakes:

• Missing leading slash in URL
• Calling .json() directly on fetch without then
• Using response.text() instead of response.json()

3. What will the following code output if the REST API returns two posts with titles 'Hello' and 'World'?

fetch('/wp-json/wp/v2/posts')
  .then(res => res.json())
  .then(posts => {
    posts.forEach(post => console.log(post.title.rendered));
  });

medium

A. undefined\nundefined

B. posts.forEach is not a function

C. Hello\nWorld

D. Error: Cannot read property 'rendered' of undefined

Solution

1. Step 1: Understand fetch and JSON parsing

   The fetch gets posts, then res.json() parses the JSON array of posts.

2. Step 2: Loop through posts and log titles

   posts.forEach logs each post's title.rendered, so it prints 'Hello' and 'World'.

3. Final Answer:

   Hello\nWorld -> Option C

4. Quick Check:

   posts.forEach + post.title.rendered = Hello and World [OK]

Hint: Use console.log inside forEach to print each post title [OK]

Common Mistakes:

• Assuming posts is not an array
• Forgetting to parse JSON with res.json()
• Accessing title without .rendered property

4. Identify the error in this code snippet that tries to fetch pages from WordPress REST API:

async function getPages() {
  const response = await fetch('wp-json/wp/v2/pages');
  const data = await response.json;
  console.log(data);
}

medium

A. The function should not be async

B. The fetch URL is missing a leading slash '/' and response.json is missing parentheses

C. console.log should be before fetch call

D. response.json should be replaced with response.text

Solution

1. Step 1: Check fetch URL format

   The URL 'wp-json/wp/v2/pages' is missing a leading slash '/' which is required for root-relative path.

2. Step 2: Check response.json usage

   response.json is a function and must be called with parentheses: response.json()

3. Final Answer:

   The fetch URL is missing a leading slash '/' and response.json is missing parentheses -> Option B

4. Quick Check:

   URL slash + response.json() needed [OK]

Hint: Always add '/' before REST API path and call .json() as function [OK]

Common Mistakes:

• Forgetting parentheses on response.json
• Missing leading slash in URL
• Misplacing console.log before data is fetched

5. You want to fetch posts and display only those with the word 'JavaScript' in the title using async/await. Which code correctly filters and logs these posts?

hard

A. async function fetchJSPosts() {
const res = await fetch('/wp-json/wp/v2/posts');
const posts = await res.text();
const filtered = posts.filter(post => post.title.rendered.includes('JavaScript'));
filtered.forEach(post => console.log(post.title.rendered));
}

B. async function fetchJSPosts() {
const res = await fetch('/wp-json/wp/v2/posts');
const posts = await res.json;
const filtered = posts.filter(post => post.title.includes('JavaScript'));
filtered.forEach(post => console.log(post.title.rendered));
}

C. async function fetchJSPosts() {
const res = await fetch('/wp-json/wp/v2/posts');
const posts = await res.json();
const filtered = posts.filter(post => post.title.rendered == 'JavaScript');
filtered.forEach(post => console.log(post.title.rendered));
}

D. async function fetchJSPosts() {
const res = await fetch('/wp-json/wp/v2/posts');
const posts = await res.json();
const filtered = posts.filter(post => post.title.rendered.includes('JavaScript'));
filtered.forEach(post => console.log(post.title.rendered));
}

Solution

1. Step 1: Correctly fetch and parse JSON

   Use await res.json() to parse the response as JSON array of posts.

2. Step 2: Filter posts by checking if title.rendered includes 'JavaScript'

   Use posts.filter with post.title.rendered.includes('JavaScript') to select matching posts.

3. Step 3: Log filtered post titles

   Use forEach to log each filtered post's title.rendered.

4. Final Answer:

   async function fetchJSPosts() { const res = await fetch('/wp-json/wp/v2/posts'); const posts = await res.json(); const filtered = posts.filter(post => post.title.rendered.includes('JavaScript')); filtered.forEach(post => console.log(post.title.rendered)); } -> Option D

5. Quick Check:

   await fetch + .json() + filter + includes = async function fetchJSPosts() { const res = await fetch('/wp-json/wp/v2/posts'); const posts = await res.json(); const filtered = posts.filter(post => post.title.rendered.includes('JavaScript')); filtered.forEach(post => console.log(post.title.rendered)); } [OK]

Hint: Use .json() and filter with includes() on title.rendered [OK]

Common Mistakes:

• Forgetting parentheses on json()
• Using == instead of includes for substring
• Parsing response as text instead of JSON