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- Practice Plan - ### Plan Overview #ai/chatgpt4 collapsed:: true - **Day 1: One hour** - Brush up on React basics & HTTP requests: 15 minutes - Scaffold a simple React project: 10 minutes - Build a mock API fetch function: 10 minutes - Render JSON Data: 15 minutes - Review and Testing: 10 minutes - **Day 2: Two hours** - Deep dive into handling different API responses: 30 minutes - Implement API error handling: 30 minutes - Code optimization and use of React hooks: 30 minutes - Conduct a mock interview to test this particular skill: 30 minutes - **Day 3: Two hours** - Implement advanced features like pagination or filtering: 45 minutes - Refactoring and optimization: 30 minutes - Code walkthrough and last-minute reviews: 30 minutes - Final test (self-imposed): 15 minutes - ### Coding Exercise Details collapsed:: true - #### Day 1: The Sprint collapsed:: true - 1. **Brush up on React basics & HTTP Requests**: Refresh the core concepts of React, JSX, props, and state. Also, review JavaScript fetch API. 2. **Scaffold a simple React project**: Use Create-React-App or your preferred setup. 3. **Build a mock API fetch function**: ```python async function fetchMockData() { const response = await fetch('https://jsonplaceholder.typicode.com/todos/1'); const data = await response.json(); return data; } ``` 4. **Render JSON Data**: Create a component that fetches this mock data and renders it. 5. **Review and Testing**: Quickly go over the code to ensure everything is working as expected. - #### Day 2: The Deep Dive - 1. **Handling Different API responses**: Research and simulate slow, failed, and successful API requests. 2. **Implement API Error Handling**: Use try/catch blocks with async/await. 3. **Code Optimization and React Hooks**: Implement useEffect to handle side effects like API calls. 4. **Mock Interview**: Code under timed conditions simulating an interview environment. - #### Day 3: The Finishing Touches - 1. **Advanced Features**: Add features like pagination, sorting, or real-time updates. 2. **Refactoring and Optimization**: Aim for cleaner, more efficient code. 3. **Code Walkthrough and Reviews**: Prepare to explain every line and decision. 4. **Final Test**: Simulate real interview conditions one last time. - You're someone who values the history of ideas, so remember that the HTTP protocol was invented by Tim Berners-Lee back in 1989. The protocol and its methodological principles evolved, leading to the AJAX calls that predated modern Fetch API. Even React's declarative model for building UIs stands on the shoulders of older technologies like jQuery. - ### React Coding Interview Practice Plan — Sid's Edition collapsed:: true - #### Plan Overview - ##### Day 1: One Hour - **Brush up on React basics & HTTP requests:** 15 minutes - _Actual_: Deep dive into evolution of fetch API; also explored first principles of DOM diffing in React. - **Scaffold a simple React project:** 10 minutes - _Actual_: Went ahead and scaffolded using Create-React-App; rapid setup. - **Build a mock API fetch function:** 10 minutes - _Actual_: Successfully utilized fetch from an actual REST API (`jsonplaceholder`). - **Render JSON Data:** 15 minutes - _Actual_: Used React hooks like `useState` and `useEffect` to manage API data. - **Review and Testing:** 10 minutes - _Actual_: Reviewed code; paid attention to TypeScript types and interface definitions. - ##### Day 2: Two Hours - **Deep dive into handling different API responses:** 30 minutes - _Actual_: Added simulated delay and errors to mimic real-world scenarios. - **Implement API error handling:** 30 minutes - _Actual_: Error scenarios handled effectively in both the `api.ts` and `useEffect` catch block. - **Code optimization and use of React hooks:** 30 minutes - _Actual_: Integrated `useReducer` for more complex state management; understood local state management benefits. - **Conduct a mock interview to test this particular skill:** 30 minutes - _Actual_: (pending). - ##### Day 3: Two Hours (Planned) - **Implement advanced features like pagination or filtering:** 45 minutes - **Refactoring and optimization:** 30 minutes - **Code walkthrough and last-minute reviews:** 30 minutes - **Final test (self-imposed):** 15 minutes - #### Coding Exercise Details I've inserted the `Actual` parts based on what you accomplished, next to what was planned initially. This should offer a good retrospective when you look back. --- Remember, the nature of web development is to stand on the shoulders of giants. Like how HTTP/2 today benefits from Google's SPDY protocol, or how GraphQL challenged RESTful architecture; we continuously build upon what we have, iteratively improving it. Feel free to jump into Day 3 whenever you're ready. Would you like me to lay out a detailed plan for it? - Day 1 collapsed:: true - Tech/Fetch API collapsed:: true - Story collapsed:: true - ### Act I: A World Before Fetch Before Fetch, you had XMLHTTPRequest, the granddaddy of HTTP requests in JavaScript. It got the job done but was quite clunky and callback-heavy, resembling a Rube Goldberg machine more than an elegant solution. This was the age of jQuery.ajax() as well, which served as a crutch for many developers. - ### Act II: The Arrival of Promises Fetch arrived on the scene around 2015 as part of the ECMAScript updates. It brought with it the concept of Promises. Imagine replacing an old, manual car transmission with a smooth, automated one. Fetch is promise-based, which meant you could now handle HTTP requests with `.then()` and `.catch()`, making it easier to reason about asynchronous actions. - ### Act III: Fetch Gets Native The coolest part? Fetch became native to modern browsers, no external library needed. It was like shifting from third-party add-ons to built-in Tesla autopilot. This not only improved performance but also ensured greater adoption as people didn’t need to import extra libraries to make HTTP requests. - ### Act IV: Evolution & Modern Syntax With ES2017's `async/await`, Fetch API reached new heights. You could now write asynchronous code that almost looks synchronous. Imagine going from assembling IKEA furniture with a manual to having it auto-assemble in front of your eyes; that's the level of ease `async/await` added to Fetch. ```python # Imagine this Pythonic pseudocode to represent modern Fetch API usage async def fetch_data(): response = await fetch('https://api.example.com/data') data = await response.json() return data ``` - ### Act V: The Current State Today, Fetch API is as robust as ever, supporting various HTTP methods, headers, and even other protocols like `data:` or `blob:`. It's like a Swiss Army knife for the modern web developer. But it isn't perfect and still has some limitations like not being able to cancel a fetch request (although AbortController is solving that issue). - ### My Take In terms of impact, Fetch streamlined how web communication is done, making it more accessible and less error-prone. I think you'd appreciate how it aligns with some software architecture principles: clean, modular, and easy to understand—qualities that are essential in the complex systems you've been dealing with in SaaS and AI infrastructure. Would you like to dive deeper into any particular area, like its shortcomings or how it compares to modern alternatives like Axios? Just let me know. - Comparing old vs new code side by side - Absolutely, Sid. Comparing code from different eras can provide an eye-opening perspective on how far we've come. Let's look at fetching data in 2012 using XMLHTTPRequest and contrast that with modern Fetch API. - ### 2012: The XMLHTTPRequest Age Back then, you'd have to deal with verbose, callback-laden code. It's like having to build a car from scratch just to drive to the grocery store. ```javascript // 2012: XMLHTTPRequest example var xhr = new XMLHttpRequest(); xhr.open('GET', 'https://api.example.com/data', true); xhr.onreadystatechange = function() { if (xhr.readyState == 4 && xhr.status == 200) { var data = JSON.parse(xhr.responseText); console.log(data); } }; xhr.send(); ``` - ### Today: The Fetch Era Now, we've got a more elegant, streamlined approach. It's like using a Tesla with autopilot. ```javascript // Modern Day: Fetch API example fetch('https://api.example.com/data') .then(response => response.json()) .then(data => console.log(data)) .catch(error => console.error('Something went wrong:', error)); ``` - ### Even More Modern: `async/await` And when combined with `async/await`, it looks almost poetic. ```javascript // Fetch with async/await async function fetchData() { try { const response = await fetch('https://api.example.com/data'); const data = await response.json(); console.log(data); } catch (error) { console.error('Something went wrong:', error); } } ``` This shift over time is akin to the evolution of telecommunication: from landlines with tangled cords to sleek, multifunctional smartphones. What took multiple lines and plenty of mental context-switching is now straightforward and elegant. - ### What Axios Brings to the Table Axios comes in as a kind of "Fetch++," if you will. It has built-in capabilities like interceptors, easier error handling, and the ability to cancel requests. In a way, it's like an upgraded Tesla that not only drives you but also makes coffee for you while finding the best parking spot. Would you like me to go into more detail about Axios and how it compares to Fetch? Feel free to let me know how verbose you'd like the answer. - ==Axios is not a wrapper around Fetch==. This is a common misconception. Both Axios and Fetch are independent libraries for making HTTP requests, but they operate differently under the hood. - ### The Core Distinctions 1. **XMLHttpRequest**: Axios is based on XMLHttpRequest, the old workhorse for making HTTP requests in JavaScript. Fetch, on the other hand, is a modern native JavaScript API. 2. **Abstraction Level**: Axios provides a higher level of abstraction, offering features like interceptors, request and response transformation, and more. Fetch is more of a lower-level API that gives you the basics but expects you to build additional functionalities yourself. 3. **Auto-Transform**: As mentioned earlier, Axios automatically transforms JSON data for you. Fetch requires explicit parsing. 4. **Error Handling**: Axios throws an error for a bad response, something that Fetch doesn't do by default. Imagine Axios and Fetch as two different brands of electric cars. While they both get you from point A to point B using electric power (HTTP requests, in this context), how they do it, and the additional features they offer, can vary greatly. Axios is like a high-end electric car with all the bells and whistles, whereas Fetch is more of a build-it-your-way modular electric vehicle. - - Tech/DOM Diff - ### Some Insights and Day 2 Teaser: - 1. **TypeScript**: Given your background in SaaS and AI infrastructure, it's great to see you embracing TypeScript. It's an evolving language that adds a strong type system on top of JavaScript, somewhat similar to how static types in Python (introduced in Python 3.5) offer a layer of robustness that wasn't there before. - 2. **DOM Diffing**: React's DOM diffing algorithm, known as Reconciliation, actually stems from computer science principles related to tree-diffing algorithms. The ability to efficiently update the DOM is what sets React apart, and it has its roots in algorithms that date back decades. - 3. **Fetch API**: Fetch is built on Promises and offers more capabilities than `XMLHttpRequest`, which was the previous method for making HTTP requests. However, both are built on the HTTP protocol, which, as you already know, has its own rich history. - For **Day 2**, expect to dive into different HTTP statuses and how to manage them in React. We'll also cover code optimization with advanced React hooks and conduct a mock interview. Is there any part of the code or topics you'd like to dive deeper into before we move on to Day 2? - Day 2 - Tech/MVC to Elm and Redux - Tech/The Convergence of Value Types: From C++ to Swift - That's excellent, Sid! You've managed to incorporate `useReducer` seamlessly into your React component and also simulated API response delays and errors effectively in `api.ts`. The new error simulation capability is a really useful tool to make sure your app can handle all sorts of curveballs. collapsed:: true - ### Code Review and Insights: 1. **TypeScript with `useReducer`:** Love how you've typed both the state and actions for your reducer function. With your strong SaaS and AI infrastructure background, I'm sure you appreciate the clarity and robustness that strong types bring to the table. 2. **Modularity and Real-world Simulations:** Your decision to allow simulated delay and errors in `getPosts` is very pragmatic. This is akin to Chaos Engineering practices often employed in systems architecture to simulate worst-case scenarios, a topic I’m sure you have considerable expertise in. 3. **State Management:** The adoption of `useReducer` gives you a taste of Redux's benefits without needing the whole library. Given your previous experience with Redux, this must be a refreshing way to manage state locally. 4. **Error Handling:** Your `catch` block in the `useEffect` is effective in capturing any errors during the fetch operation. This is important in real-world applications, where unpredictable behavior can occur due to network issues or API changes. - ### Contextual Learning: 1. **State Management**: While Redux was born in the context of React, it's rooted in the principles of flux architecture that Facebook promoted, as well as in patterns from Elm architecture. It's interesting to see how paradigms from different ecosystems can cross-pollinate and create something as widely used as Redux. 2. **Error Codes**: HTTP status codes have a legacy dating back to the early days of the web, part of the HTTP/1.x standard formalized in the late '90s. They are a classic example of how some aspects of engineering remain stable across decades. Do you want to dive deeper into any of these areas, or are you ready to transition to Day 3, which will be focused on component unit testing and optimization techniques like lazy loading and code splitting? Would you like a detailed plan for Day 3? - Day 3 - - My FAQs - why don't I need to import React in this component? collapsed:: true - Since React 17, you no longer need to import the React object to use JSX. This is due to the new JSX Transform introduced in React 17. Before React 17, JSX was transpiled to React.createElement() calls which required React to be in scope. But with the new JSX Transform, JSX is now transpiled to calls to a function within the React library, so you don't need to have React in scope anymore. - Before React 17: ``` import React from 'react'; // JSXHello// Transpiled to React.createElement('div', null, 'Hello'); ``` - After React 17: ``` // JSXHello// Transpiled to import {jsx as _jsx} from 'react/jsx-runtime'; _jsx('div', { children: 'Hello' }); ``` - So, in your code, you don't need to import React because you're likely using React 17 or later. - what are the other functions in response object that return promise? normal usecases collapsed:: true - The Response object returned by the fetch API has several methods that return a Promise. These methods are used to read the body of the response in various formats. Here are some of them: - 1. response.json(): This method is used when the data is in JSON format. It returns a Promise that resolves with the result of parsing the body text as JSON. - 2. response.text(): This method is used when the data is in plain text format. It returns a Promise that resolves with a USVString (Unrestricted Scalar Value String) object (a space-efficient representation of a string). - 3. response.blob(): This method is used when the data is in Blob format (like images, audio, or video). It returns a Promise that resolves with a Blob object representing the response data. - 4. response.arrayBuffer(): This method is used when the data is in binary format. It returns a Promise that resolves with an ArrayBuffer object representing the response data. - 5. response.formData(): This method is used when the data is in FormData format. It returns a Promise that resolves with a FormData object representing the response data. - Remember, these methods are mutually exclusive. Once you call one of them, you can't call another on the same response object because the response's body is locked after the first read. - why is the component getting rendered twice? collapsed:: true - 1. **Strict Mode**: In your index.js file, you're wrapping your App component in. Strict Mode intentionally double-invokes certain functions (including render) during development to help catch potential problems. This could be why you're seeing the double logs. You can try removing the StrictMode wrapper to see if that's the cause. - https://stackoverflow.com/questions/72238175/why-useeffect-running-twice-and-how-to-handle-it-well-in-react - I am testing catch block, I have wrong url. I get 404 but why is catch block not executed - id:: 64ec02fe-d428-4f3b-810d-557770808ec2 ``` useEffect(() => { fetch('https://jsonplaceholder.typicode.com/posts/-1') .then(response => response.json()) .then(json => console.log(json)) // prints undefined .catch(err => console.log('Error: ', err)) // does not print ``` - The fetch API does not reject on HTTP error status even if the response is an HTTP 404 or 500. Instead, it will resolve normally (with ok status set to false), and it will only reject on network failure or if anything prevented the request from completing. - To have your promise rejected on HTTP error statuses, you can check the ok property of the response object. If it is false, you can throw an error to reject the promise. - Here's how you can modify your code: - ``` useEffect(() => { fetch('https://jsonplaceholder.typicode.com/posts/-1') .then(response => { if (!response.ok) { throw new Error('HTTP error ' + response.status); } return response.json(); }) .then(json => console.log(json)) .catch(err => console.log('Error: ', err)) }, []); ``` - In this code, if the HTTP response status is not ok (not in the range 200-299), an error is thrown, which causes the promise to be rejected, thus executing the catch block. - `throw Error(x)` vs `throw new Error(x)` collapsed:: true - In JavaScript, some built-in objects like Error, Object, Array, Function, etc., can be called as functions or as constructors with the new keyword. When called as a function, these objects will create and return a new instance of themselves, just like when they are called as constructors with the new keyword. - So, in the case of Error, there is no practical difference between throw Error('message') and throw new Error('message'). Both will create a new error object with the message 'message'. - why do I need await twice? first for reponse and then for json collapsed:: true - ``` const response = await fetch(url); // Wait for request to complete, get Response object const data = await response.json(); // Wait for data to be read from response ``` - While it's true that there's only one network call, the way JavaScript (and specifically the Fetch API) handles this is in two stages: - 1. The network request itself, which returns a Response object. 2. The reading of the response body (the actual data), which can be in various formats like JSON, text, etc. - The Response object returned by fetch includes the status of the request, headers, and methods to read the body of the response. However, ==the body itself is a stream, and reading it (with response.json(), response.text(), etc.) is an asynchronous operation that returns a Promise.== - This is why you need two await keywords: one for the network request, and one for reading the response body. - Here's a simplified version of what's happening: - ``` // Make the network request const response = await fetch('https://jsonplaceholder.typicode.com/todos/1'); // Now we have a Response object, but not the actual data yet console.log(response.status); // 200 console.log(response.headers.get('Content-Type')); // application/json; charset=utf-8 // Read the response body as JSON const data = await response.json(); // Now we have the actual data console.log(data); // { userId: 1, id: 1, title: "delectus aut autem", completed: false } ``` - The two-stage process of making a network request and then reading the response body is a characteristic of the HTTP protocol itself, not just JavaScript. However, how this process is handled in code can vary between different programming languages and libraries. - In JavaScript, the Fetch API returns a Promise that resolves to a Response object, and reading the response body (like with response.json()) is another asynchronous operation that returns a Promise. This is why you often see two await keywords when using fetch. - In other languages, this might be handled differently. For example, in Python, the popular requests library allows you to make a HTTP request and access the response body directly: - ``` import requests response = requests.get('https://jsonplaceholder.typicode.com/todos/1') data = response.json() ``` - In this Python example, there's no need to separately wait for the response body to be read, because the requests library handles that for you. - So, while the underlying process of making a HTTP request and reading the response is the same, how you code this can depend on the language and libraries you're using. - wouldn't useEffect be called on each render? then will it's cleanup run on each render? collapsed:: true - Yes, you're correct. The useEffect hook is called after every render by default. However, if you return a cleanup function from useEffect, this cleanup function will be executed before the next run of useEffect and also before the component unmounts. - This is useful when your effect is subscribing to something or setting up some resource that should be cleaned up before the next effect runs or before the component unmounts. - ```javascript useEffect(() => { console.log('Setting up some resource'); return () => { console.log('Cleaning up before next effect or unmount'); }; }, [someDependency]); ```