Fix for Wai Hoi’s PR proofreading

README.md

@@ -1,16 +1,16 @@
 Introduction to Front End at Grab
 ==
 
-Front end development has never been so complex and exciting in the history of web development. New tools, libraries, frameworks and plugins emerge every other day and there is so much to learn. Fortunately, or unfortunately, at Grab, the web team has been [keeping up](https://blog.daftcode.pl/hype-driven-development-3469fc2e9b22) with the latest best practices and has incorporated the modern JavaScript ecosystem in our web apps.
+Front end development has never been so complex and exciting as it is today. New tools, libraries, frameworks and plugins emerge every other day and there is so much to learn. Fortunately, or unfortunately, at Grab, the web team has been [keeping up](https://blog.daftcode.pl/hype-driven-development-3469fc2e9b22) with the latest best practices and has incorporated the modern JavaScript ecosystem in our web apps.
 
-The result of this is that our new hires or back end engineers, who are not necessarily well-acquainted with the modern JavaScript ecosystem, may feel overwhelmed by the barrage of new things that they have to learn just to complete their feature or bug fix in a web app. It is imperative that they are guided to embrace this evolution of the front end, learn to navigate the ecosystem with ease, and get productive in shipping code to our users as fast as possible. We the web team, have come up with a study guide to introduce why we do what we do.
+The result of this is that our new hires or back end engineers, who are not necessarily well-acquainted with the modern JavaScript ecosystem, may feel overwhelmed by the barrage of new things that they have to learn just to complete their feature or bug fix in a web app. It is imperative that they are guided to embrace this evolution of the front end, learn to navigate the ecosystem with ease, and get productive in shipping code to our users as fast as possible. We have come up with a study guide to introduce why we do what we do.
 
-This study guide is inspired by ["A Study Plan to Cure JavaScript Fatigue"](https://medium.freecodecamp.com/a-study-plan-to-cure-javascript-fatigue-8ad3a54f2eb1#.g9egaapps) and is mildly opinionated in the sense that we recommend certain libraries/frameworks to learn for each aspect of front end development, based on what is currently evaluated to be the most suitable to be used at Grab. We explain why a certain library is chosen and provide links to learning resources to enable the reader to pick it up on their own. Alternative choices that may be better for other use cases are provided as well for reference and further self-exploration.
+This study guide is inspired by ["A Study Plan to Cure JavaScript Fatigue"](https://medium.freecodecamp.com/a-study-plan-to-cure-javascript-fatigue-8ad3a54f2eb1#.g9egaapps) and is mildly opinionated in the sense that we recommend certain libraries/frameworks to learn for each aspect of front end development, based on what is currently deemed most suitable at Grab. We explain why a certain library is chosen and provide links to learning resources to enable the reader to pick it up on their own. Alternative choices that may be better for other use cases are provided as well for reference and further self-exploration.
 
 **Pre-requisites**
 
 - Good understanding of core programming concepts.
-- Comfortable with basic command line actions and familiarity with source code version control system such as Git.
+- Comfortable with basic command line actions and familiarity with source code version control systems such as Git.
 - Experience in web development. Have built server-side rendered web apps using frameworks like Ruby on Rails, Django, Express, etc.
 - Understanding of how the web works. Familiarity with web protocols and conventions like HTTP and RESTful APIs.
 
@@ -60,7 +60,7 @@ JavaScript frameworks have been created to provide higher-level abstractions ove
 
 Before you dive into the various aspects of building a JavaScript web app, it is important to get familiar with the language of the web - JavaScript, or ECMAScript. JavaScript is an incredibly versatile language which you can also use to build [web servers](https://nodejs.org/en/), [native mobile apps](https://facebook.github.io/react-native/) and [desktop apps](https://electron.atom.io/).
 
-Prior to 2015, the last major update was ECMAScript 5.1, in 2011. However, in the recent years, JavaScript has suddenly seen a huge burst of improvements within a short span of time. In 2015, ECMAScript 2015 (previously called ECMAScript 6) was released and a huge ton of syntactic constructs were introduced to make writing code less unwieldy. Auth0 has written a [nice history of JavaScript](https://auth0.com/blog/a-brief-history-of-javascript/). Till this day, not all browsers have fully implemented the ES2015 specification. Tools such as [Babel](https://babeljs.io/) enable developers to write ES2015 in their apps and Babel transpiles them down to ES5 to be compatible for browsers.
+Prior to 2015, the last major update was ECMAScript 5.1, in 2011. However, in the recent years, JavaScript has suddenly seen a huge burst of improvements within a short span of time. In 2015, ECMAScript 2015 (previously called ECMAScript 6) was released and a ton of syntactic constructs were introduced to make writing code less unwieldy. Auth0 has written a [nice history of JavaScript](https://auth0.com/blog/a-brief-history-of-javascript/). Till this day, not all browsers have fully implemented the ES2015 specification. Tools such as [Babel](https://babeljs.io/) enable developers to write ES2015 in their apps and Babel transpiles them down to ES5 to be compatible for browsers.
 
 Being familiar with both ES5 and ES2015 is crucial. ES2015 is still relatively new and a lot of open source code and Node.js apps are still written in ES5. If you are doing debugging in your browser console, you might not be able to use ES2015 syntax. On the other hand, documentation and example code for many modern libraries that we will introduce later below are written in ES2015. At Grab, we use ES2015 (with [Babel Stage-0 preset](https://babeljs.io/docs/plugins/preset-stage-0/)) to embrace the syntactic improvements the future of JavaScript provides and we have been loving it so far.
 
@@ -84,11 +84,11 @@ React brings about many radical ideas and encourages developers to [rethink best
 
 - **Functional** - The view is a pure function of `props` and `state`. In most cases, a React component is defined by `props` (external parameters) and `state` (internal data). For the same `props` and `state`, the same view is produced. Pure functions are easy to test, and the same goes for functional components. Testing in React is made easy because a component's interfaces are well-defined and you can test the component by supplying different `props` and `state` to it and comparing the rendered output.
 
-- **Maintainable** - Writing your view in a component-based fashion encourages reusability. We find that defining a component's `propTypes` make React code self-documenting as the reader can know clearly what is needed to use that component. Lastly, your view and logic is self-contained within the component, and should not be affected nor affect other components. It is thus easy to shift components around during large-scale refactoring, as long as the same `props` are supplied to the component.
+- **Maintainable** - Writing your view in a component-based fashion encourages reusability. We find that defining a component's `propTypes` make React code self-documenting as the reader can know clearly what is needed to use that component. Lastly, your view and logic is self-contained within the component, and should not be affected nor affect other components. That makes it easy to shift components around during large-scale refactoring, as long as the same `props` are supplied to the component.
 
 - **High Performance** - You might have heard that React uses a virtual DOM (not to be confused with [shadow DOM](https://developer.mozilla.org/en-US/docs/Web/Web_Components/Shadow_DOM)) and it re-renders everything when there is a change in state. Why is there a need for a virtual DOM? While modern JavaScript engines are fast, reading from and writing to the DOM is slow. React keeps a lightweight virtual representation of the DOM in memory. Re-rendering everything is a misleading term. In React it actually refers to re-rendering the in-memory representation of the DOM, not the actual DOM itself. When there's a change in the underlying data of the component, a new virtual representation is created, and compared against the previous representation. The difference (minimal set of changes required) is then patched to the real browser DOM.
 
-- **Ease of Learning** - Learning React is pretty simple. The React API surface is relatively small as compared to [this](https://angular.io/docs/ts/latest/api/); there are only a few APIs to learn and they do not change often. The React community is one of the largest, and along with that comes a vibrant ecosystem of tools, open-sourced UI components, and a ton of great resources online to get you started on learning React.
+- **Ease of Learning** - Learning React is pretty simple. The React API surface is relatively small compared to [this](https://angular.io/docs/ts/latest/api/); there are only a few APIs to learn and they do not change often. The React community is one of the largest, and along with that comes a vibrant ecosystem of tools, open-sourced UI components, and a ton of great resources online to get you started on learning React.
 
 - **Developer Experience** - There are a number of tools that improves the development experience with React. [React Devtools](https://github.com/facebook/react-devtools) is a browser extension that allows you to inspect your component, view and manipulate its `props` and `state`. [Hot reloading] with webpack allows you to view changes to your code in your browser, without you having to refresh the browser. Front end development involves a lot of tweaking code, saving and then refreshing the browser. Hot reloading helps you by eliminating the last step. When there are library updates, Facebook provides [codemod scripts](https://github.com/reactjs/react-codemod) to help you migrate your code to the new APIs. This makes the upgrading process relatively pain-free. Kudos to the Facebook team for their dedication in making the development experience with React great.
 
@@ -168,7 +168,7 @@ Code is read more frequently than it is written. This is especially true at Grab
 
 ### Testing - Jest + Enzyme
 
-[Jest](http://facebook.github.io/jest/) is a testing library by Facebook that aims to make the process of testing pain-free. As with Facebook projects, it provides a great development experience out of the box. Tests can be run in parallel for faster speed and during watch mode, only the tests for the changed files are ran. One particular feature we like is "Snapshot Testing". Jest can save the generated output of your React component and Redux state and save it as serialized files, so you wouldn't have to manually come up with the expected output yourself. Jest also comes with built-in mocking, assertion and test coverage. One library to rule them all!
+[Jest](http://facebook.github.io/jest/) is a testing library by Facebook that aims to make the process of testing pain-free. As with Facebook projects, it provides a great development experience out of the box. Tests can be run in parallel for faster speed and during watch mode, only the tests for the changed files are run. One particular feature we like is "Snapshot Testing". Jest can save the generated output of your React component and Redux state and save it as serialized files, so you wouldn't have to manually come up with the expected output yourself. Jest also comes with built-in mocking, assertion and test coverage. One library to rule them all!
 
 React comes with some testing utilities, but [Enzyme](http://airbnb.io/enzyme/) by Airbnb makes it easier to generate, assert, manipulate and traverse your React components' output with a jQuery-like API. It is recommended that Enzyme be used to test React components.
 
@@ -192,7 +192,7 @@ The documentation for Jest and Enzyme are pretty concise, and it should be suffi
 
 ### Linting - ESLint
 
-A linter is a tool to statically analyze code and finds problems with it, potentially preventing bugs/runtime errors and at the same time, enforcing a coding style. Time is saved during pull request reviews when reviewers do not have to leave nitpicky comments on coding style. [ESLint](http://eslint.org/) is a tool for linting JavaScript code that is highly extensible and customizable. Teams can write their own lint rules to enforce their custom styles. At Grab, we use Airbnb's [`eslint-config-airbnb`](https://www.npmjs.com/package/eslint-config-airbnb) preset, that has already been configured with the common good coding style in the [Airbnb JavaScript style guide](https://github.com/airbnb/javascript).
+A linter is a tool to statically analyze code and finds problems with them, potentially preventing bugs/runtime errors and at the same time, enforcing a coding style. Time is saved during pull request reviews when reviewers do not have to leave nitpicky comments on coding style. [ESLint](http://eslint.org/) is a tool for linting JavaScript code that is highly extensible and customizable. Teams can write their own lint rules to enforce their custom styles. At Grab, we use Airbnb's [`eslint-config-airbnb`](https://www.npmjs.com/package/eslint-config-airbnb) preset, that has already been configured with the common good coding style in the [Airbnb JavaScript style guide](https://github.com/airbnb/javascript).
 
 For the most part, using ESLint is as simple as tweaking a configuration file in your project folder. There's nothing much to learn about ESLint if you're not writing new rules for it. Just be aware of the errors when they surface and Google it to find out the recommended style.
 
@@ -214,7 +214,7 @@ Static typing brings about many benefits when writing apps. They can catch commo
 
 Adding types to your code comes with the tradeoff of increased verbosity and a learning curve of the syntax. But this learning cost is paid upfront and amortized over time. In complex projects where the maintainability of the code matters and the people working on it change over time, adding types to the code brings about more benefits than disadvantages.
 
-The two biggest contenders in adding static types for JavaScript are [Flow](https://flow.org/) (by Facebook) and [TypeScript](https://www.typescriptlang.org/) (by Microsoft). As of date, there is no clear winner in the battle. For now, we have made the choice of using Flow. We find that Flow has a lower learning curve as compared to TypeScript and it requires relatively less effort to migrate an existing code base to Flow. Being built by Facebook, Flow has better integration with the React ecosystem out of the box. Anyway, it is also not extremely difficult to move from Flow to TypeScript as the syntax and semantics are quite similar, and we will re-evaluate the situation in time to come. After all, using one is better than not using at all.
+The two biggest contenders in adding static types for JavaScript are [Flow](https://flow.org/) (by Facebook) and [TypeScript](https://www.typescriptlang.org/) (by Microsoft). As of date, there is no clear winner in the battle. For now, we have made the choice of using Flow. We find that Flow has a lower learning curve as compared to TypeScript and it requires relatively less effort to migrate an existing code base to Flow. Being built by Facebook, Flow has better integration with the React ecosystem out of the box. Anyway, it is not extremely difficult to move from Flow to TypeScript as the syntax and semantics are quite similar, and we will re-evaluate the situation in time to come. After all, using one is better than not using any at all.
 
 Flow recently revamped their documentation site and it's pretty neat now!
 
@@ -291,11 +291,11 @@ The most common Yarn commands can be found [here](https://yarnpkg.com/en/docs/us
 
 ### The Journey has Just Begun
 
-Congratulations on making it this far! Front end development now is [hard](https://hackernoon.com/how-it-feels-to-learn-javascript-in-2016-d3a717dd577f), but it is also more interesting than before. What we have covered so far will help any new engineer to Grab's web team to get up to speed with our technologies pretty quickly. There are many more things to be learnt, but building up a solid foundation in the essentials will aid in learning the rest of the technologies. This helpful [front end web developer roadmap](https://github.com/kamranahmedse/developer-roadmap#-front-end-roadmap) shows the alternative technologies available for each aspect.
+Congratulations on making it this far! Front end development today is [hard](https://hackernoon.com/how-it-feels-to-learn-javascript-in-2016-d3a717dd577f), but it is also more interesting than before. What we have covered so far will help any new engineer to Grab's web team to get up to speed with our technologies pretty quickly. There are many more things to be learnt, but building up a solid foundation in the essentials will aid in learning the rest of the technologies. This helpful [front end web developer roadmap](https://github.com/kamranahmedse/developer-roadmap#-front-end-roadmap) shows the alternative technologies available for each aspect.
 
 We made our technical decisions based on what was important to a rapidly growing Grab Engineering team - maintainability and stability of the front end code base. These decisions may or may not apply to smaller teams and projects. Do evaluate what works best for you and your company.
 
-As the front end ecosystem grows, we are actively exploring, experimenting and evaluating how new technologies can make us a more efficient team and improve our productivity. We hope that this post has given you insights on the front end technologies we use at Grab. If what we are doing interests you, [we are hiring](https://grab.careers)!
+As the front end ecosystem grows, we are actively exploring, experimenting and evaluating how new technologies can make us a more efficient team and improve our productivity. We hope that this post has given you insights into the front end technologies we use at Grab. If what we are doing interests you, [we are hiring](https://grab.careers)!
 
 ### More Reading