REST API with JavaScript in Wordpress - Step-by-Step Execution

Concept Flow - REST API with JavaScript

Start

↓

Create fetch request

↓

Send request to REST API

↓

Wait for response

↓

Check response status

↓

Parse JSON

↓

Use data

↓

End

This flow shows how JavaScript sends a request to a REST API, waits for the response, checks if it is successful, then parses and uses the data or handles errors.

Execution Sample

Wordpress

fetch('https://example.com/wp-json/wp/v2/posts')
  .then(response => {
    if (!response.ok) {
      throw new Error(`HTTP error! status: ${response.status}`);
    }
    return response.json();
  })
  .then(data => console.log(data))
  .catch(error => console.error('Error:', error));

This code fetches posts from a WordPress REST API, converts the response to JSON, logs the data, and handles errors.

Execution Table

Step	Action	Evaluation	Result
1	Call fetch with URL	Request sent to https://example.com/wp-json/wp/v2/posts	Promise pending
2	Receive response	Response status 200 OK	Promise resolved with response
3	Call response.json()	Parse JSON body	Promise resolved with data array
4	Call console.log(data)	Output data to console	Data displayed in console
5	If error occurs	Catch block runs	Error message logged

💡 Fetch completes after data is logged or error is handled

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
response	undefined	Response object with status 200	undefined	undefined
data	undefined	undefined	Array of posts JSON	Array of posts JSON
error	undefined	undefined	undefined	Error object if any

Key Moments - 3 Insights

Why do we use .then() after fetch?

Because fetch returns a Promise, .then() waits for the response before continuing, as shown in steps 2 and 3 of the execution_table.

What happens if the API returns an error status?

The catch block runs to handle errors, as shown in step 5 of the execution_table, preventing the app from crashing.

Why do we call response.json()?

Because the response body is a stream, response.json() reads and parses it into usable JavaScript data, shown in step 3.

Visual Quiz - 3 Questions

Look at the execution_table, what is the state of the fetch promise after step 1?

A Pending

B Resolved with data

C Rejected with error

D Undefined

💡 Hint

Check the 'Result' column in step 1 of the execution_table

At which step is the JSON data available to use?

A Step 1

B Step 3

C Step 2

D Step 5

💡 Hint

Look at the 'Evaluation' and 'Result' columns in the execution_table

If the API URL is wrong, which step will handle the problem?

A Step 2

B Step 4

C Step 5

D Step 3

💡 Hint

Refer to the 'Action' and 'Result' columns for error handling in the execution_table

Concept Snapshot

REST API with JavaScript:
- Use fetch('URL') to request data
- fetch returns a Promise
- Use .then() to wait for response
- Call response.json() to parse data
- Use .catch() to handle errors
- Data can then be used in your app

Full Transcript

This lesson shows how JavaScript talks to a REST API, like WordPress's API, using fetch. First, fetch sends a request to the API URL. Then it waits for the server to respond. When the response arrives, we check if it is successful. If yes, we convert the response to JSON format to get the data. We then use the data, for example, by showing it in the console. If there is an error at any point, we catch it and show an error message. This flow helps your app get data from servers safely and clearly.