Beginners Guide To React

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The beginners

GUIDE TO
REACT &
REDUX
The Complete React Web
Development Course (with Redux)

In this section we will dive into the very basic fundamentals of
React and setting up your own web developer environment to

Section 1

React 101
• Install Visual Studio Code

write and execute your own code. We will go through installing a
very popular text editor release by Microsoft called Visual Studio
Code to installing Node.js on your machine and then onto setting
up your very own local web server and installing Babel.
Once we have setup your developer environment we will continue
to learn the fundamentals of JavaScript (ES6) and JSX syntax to
build our foundational skills on both languages and technologies

• Install Node.js

on which the React Library is built upon.

• Setting up a Web Server

After learning the basics we will move onto the next sections where

• Setting Up Babel

architecture and will build our own applications.

we will start learning more about the React component

• Exploring JSX & JSX Expressions

It will soon become apparent why React is considered a very

• ES6 Variables & Arrow Functions

popular frontend JavaScript library as you are not required to learn

• Manual Data Binding

on components.

• Forms & Input
• Arrays in JSX

a new language but rather learn an application architecture based

Installing Visual Studio Code
There are many free and paid text editors out there available to download and
use to write your own code, popular editors include Atom, Sublime Text,
Notepad++ and Visual Studio Code to name a few. We will be using Visual
Studio code as our text editor of choice to write our code as it allows us to
install some useful packages to help write our code.

To install Visual Studio code simply visit the following website and download and install the application onto your
machine: https://code.visualstudio.com/
Visual Studio Code has some useful extensions which you can install:
• Bracket Pair Colorizer
• ES7 React/Redux/GraphQL/React-Native Snippet
• Liver Server
• Prettier - Code Formatter
• Babel ES6/ES7

Installing Node.js
Node is JavaScript on the server. You can visit the following website to
download node onto your machine: https://nodejs.org/en/
Download the latest version of node that is available on their website.
To check that you have node.js installed on your machine, simply open up your terminal

and enter the following

command:
$ node —v
This will allow us to double check that node was installed onto our machine as we now have this new command and it also
shows us what version of node you have installed on your machine. When installing node we also got NPM (node package
manager) which allows us to install various dependencies/packages such as React or Yarn and other libraries. NPM and Yarn
aims to do the same job. To check that you have npm installed enter the following command in your terminal:
$ nom —v
To install yarn on your machine globally run the following command in your terminal:
$ npm install —g yarn
On windows machines you will need to restart your machine to complete the installation. To check that yarn has installed
successfully, run the following code in your terminal:
$ yarn ——version

Setting up a web server
To setup a developer web server we can achieve this in two ways using live-server.
Firstly you will need to create a directory (folder) for your application. This folder will act as a place for all your project code.
This folder can be called anything for example ‘indecision-app’. In this example we will create a sub-folder called public and
store our basic HTML file.
If we open VS Code and have installed live-server extension we can simply open up our html document and right-click to
open the file with live-server. Every-time we update our project files in the folder, the live-server will refresh the browser
which will update our application with the changes automatically.
Alternatively, we can use npm or yarn to install live-server globally onto our machines using either command in the terminal:
$ npm install —g live-server

or

$ yarn global add live-server

To check that we have installed live-server on our machine correctly we would run the command:
$ live-server —v
To run live server from the terminal, navigate to your file directory using cd and the file path. Note: you can use cd to change
directory, ls (or dir on windows) to list all the files within the folder. You can use cd ~ to navigate back to your user folder.
Once you have navigated to your project directory run the following code:
$ live-server public
Note: you would run live-server followed by the folder name in the directory you wish to serve through the live web server
(in our example we had a sub-folder called public which contained our HTML file). Any changes made in the folder will
automatically update in the browser.

Setting up Babel
Babel is a compiler and allows you to write for example JSX, ES6, ES7 code and have it compile down to regular ES5 code,
allowing your code to work on browsers which only support ES5 syntax.
https://babeljs.io/
Babel on its own has no functionality. Babel is a compiler but its not going to compile anything by default. We have to add
various plugins and presets in order to get any sort of change in our code (e.g. taking JSX code and converting it into ES5
createElement calls). A preset is just a group of plugins.
We are going to install babel locally on our machines so that when we write our code in JSX/ES6/ES7 it will compile locally
to our ES5 code (i.e. we want to write our code locally on our machine and update without using Babel on the web).
The babel website has a docs page which provide documentation on plugins available to you to install. We will install two
presets: react preset and env preset. These presets have all the necessary plugins we require and we would not need to
install the plugins individually by ourselves (as this could get out of hand very quickly). The env preset will include ES2015,
ES2016 and ES2017 plugins which will give us access to the new JavaScript features (e.g. arrow functions, const and let
variables, spread operator etc).
In our local environment we are going to install three things:
Babel itself, env preset and react preset.
In your terminal run the following command to install babel @v6.24.1 globally on your machine.
$ npm install —g babel-cli@6.24.1 or

$yarn global add babel-cli@6.24.1

This will give us a new command in our terminal which we can run while in our project directory. Run the following code to
check if Babel has been installed successfully. This should print out the help output in your terminal and will indicate if Babel
has been installed successfully on your local machine.
$ babel ——help
To clear the terminal enter the command line:
$ clear
The react and env presets will be installed locally in our projects (i.e. these codes will live in our projects so that babel CLI
can take advantage of these codes to transform our code down to ES5 syntax). Within the project directory enter the
following command:
$ npm init

or

$ yarn init

This command will setup our project to use node/yarn and specify the local dependencies. This will walk us through series of
questions such as the app name, version, description,
entry point, repository, author and license (MIT).
All this does is, it generates a brand new file in our
project called package.json (note we could have created
this file ourselves without the npm/yarn init command).
The whole point of package.json is to outline all the
dependencies that the project needs in order to run. This
will make it easy to install everything.
We are going to add our dependencies to this package.json file using the following commands in the terminal:
$ npm install babel-preset-react@6.24.1 babel-preset-env@1.5.2
$ yarn add babel-preset-react@6.24.1 babel-preset-env@1.5.2

or

This will install the two dependencies and will update the package.json file in our app folder which will now list our
dependencies for our app. Notice that a new folder has been created called node_modules. This is where all the modules
and dependencies will live.
The dependencies will have their own package.json file which will
list the dependencies they require to run. This will install the all the
sub-dependencies of their own in the node_modules folder. The
package.json file makes it easy to install all the dependencies and
sub-dependencies your application will need.
We will never need to go into the node_modules folder to change
any of the code. This folder is a auto-generated folder from the
package.json file and we can always delete and reinstall this folder/modules using the dependencies information from the
package.json file (we would use the command $ npm install or $ yarn install to install the node_modules folder again).
This command has also generated a package-lock.json file (if you used yarn this file will be called yarn.lock) in our project
folder. We will not need to edit/manually change this file. This file lists out all the dependencies in the node_module folder,
the version used and where exactly it got that package from. This helps npm/yarn behind the scenes.
We are now able to use Babel locally on our machines within our project directory to compile our React JSX code into
regular ES2015 code. In the terminal we will need to run the following command with a few arguments:
$ babel src/app.js ——out—file=public/scripts/app.js ——presets=env, react ——watch
The first argument specifies the path to our code we wan to compile (in our example above it lives in the src folder and the
file is called app.js).
The second argument specifies the output file (in our example above it lives in the public/scripts folder and is also called
app.js). This file will always be overridden by Babel.
The third argument specifies the presets we would like to use (this is a comma separated list of the presets we wish to use).
Finally, the last argument will watch for any changes in the first specified file to update (compile) the second specified file
automatically.
Babel will compile the JSX/ES6/ES7 code in one file into regular ES2015 code the browser will understand in the other file.

Exploring JSX
In JSX you can only have a single root element. If you want to add more elements side by side we will need to wrap it within
a single root element for example:
var template = 
Header Text
Paragraph Text
;
var appRoot = document.getElementById(‘app’);
ReactDOM.render(template, appRoot);
When we are creating JSX expressions, we can get really complex expressions to include a lot of information/nested
elements - however, we must have a single root element.
We can make our JSX expression more readable by formatting the elements on separate lines i.e. format as we would do in
our html code for example:
var template = (

Header Text
Paragraph Text

);
The above would still be seen as valid JSX expression and table will successfully render the expression down to ES2015.

The above is more readable to the eye and easily understood. We can make the expression even more complex and as long
as there is a single parent root element (the 
 wrapper) then this will be seen by Babel as valid JSX. Below is another
example of a complex JSX expression with nested elements.
var template = (

Header Text
Paragraph Text

Item One
Item Two


);
All this is doing is creating nested React.createElement() functions calls to create each element in the ES2015 syntax.
React.createElement(‘ol‘, null,
React.createElement(‘li’, null, ‘Item One’),
React.createElement(‘li’, null, ‘Item Two’)
)
This is why we do not write our React code in React.createElement calls as it is difficult to read and write, instead we use JSX.

We can make our JSX code dynamic by using variables to store data and then referencing these variables within our JSX
expressions. For Example:
var userName = ‘John Doe’;
var template = (

 { userName .toUpperCase()} 

We use the curly brackets to write any JavaScript expressions. Therefore we can enter the JavaScript variable within the curly
braces to output the variable value in our JSX code. This allows our JSX to be dynamic rather than static.
In our JavaScript expressions we can use different types such as strings, numbers, operators, arrays, objects, functions etc.
To render an object in React we must specify the object property, for example:
var user { name: ‘John Doe’, age: 28, location: ‘Derby’ } ;
var template = (

 Name: { user.name } 
 Age: { user.age } 
 Location: { user.location } 

);
We have now dynamically injected our data from our variables into our JSX expression.

We should now have knowledge on how to use JavaScript expression in React, how to render JavaScript strings and number
types and that we cannot render object but we can render the object properties.
There are still many more other JavaScript types. We are going to continue to look at JavaScript expressions and how we
can make truly dynamic and useful JSX.
Conditional Rendering and conditional logic in general is at the very core of software development. The same will be true
for our React interfaces for example, is the user logged into the app? If true, then show the logout button, else show the
login button.
To perform Conditional rendering in our JSX we will need to use JavaScript expressions. We can continue using the regular
conditional statements we have been using in vanilla JavaScript and do not need to learn any weird syntax.
The conditional JavaScript tools that are available are:
1) If Statements.
2) Ternary operators.
3) Logical and operator.
IF STATEMENTS:
A if statement is not an expression and therefore cannot live inside the curly brackets (i.e. JavaScript expression). However,
calling a function is an expression. We can add whatever we want in our function including if statements. The return value
from the function will show up in the JSX. For example:
var user = {
user: ‘John Doe’,
age: 28,
location: ‘Derby’
}

function getLocation(){
if (location) {
return location;
} else {
return ‘unknown’;
}
};
var template = (
 
 { getLocation(user.location) } 
 
);
We can use the function to operate the if statement and whatever is returned from our function can be used in our
JavaScript expression to pass the data into our JSX to display.
We can use other JSX expression such as {123} and {
Heading 3
} and this will render in our browser. This is
equivalent to writing JSX expression outside of the curly brackets. This is useful as it allows us to setup getLocation() to
return a separate JSX expression. For example:
function getLocation(){
if (location) {
 { getLocation(user.location) } 
} else {

return undefined;
}
};
var template = (
 { getLocation(user.location) } 
);
Important Note: undefined is implicitly returned if you do not explicitly return it. Therefore the above getLocation() function
can be simplified without returning the else statements:
function getLocation(){
if (location) {
 { getLocation(user.location) } 
}
};
This will implicitly return undefined when the statement returns false. If the Statement returns true this will return the JSX
expression value within the other JSX expression curly brackets. This will then render in our browser.
TERNARY OPERATORS:
A ternary operator is a expression and not a statement and therefore we do not need to add it to a function. A ternary
operator allows us to write if statements more concisely. For example:
True ? ‘Return True’ : ' Return False’;

[This will return ‘Return True’ as the statement is true]

False ? ‘Return True’ : ' Return False’;

[This will return ‘Return False’ as the statement is false]

These two ternary operator will check whether the statement is true or false. If true it will return the first value else it will
return the false value. Therefore the first example will return ‘Return True’ while the second example will return ‘Return False’.
We use the ? to return something when the statement equates to true while we use the : to return something when the
statement equates to false.
The first part of the ternary operator is the statement we wish to check the value i.e. whether it will return true or false.
Depending on the answer we want to return the first value else we return the second value. For example:
{ app.option.length >0 ? 
’Here are your options’
 : 
’No options’
 }
LOGICAL AND OPERATOR:
Much like the undefined, null and the boolean values true and false are all ignored by JSX. Therefore we can write a JSX
expression of {true}, {false}, {null} or {undefined} and all will be ignored by JSX and will not be rendered on the screen. This is
a very useful feature.
If we want to display a JSX expression e.g. 
 tag for age, only if the user is 18yrs or older else we do not want to display
the age of the use if they are under age. We could use the function technique, however, we are going to explore this new
technique which is just as concise as the ternary operator.
The Logical And Operator uses the && to check if two arguments returns true to run the code. If both do not return true we
do not want to run the code. We will examine the Logical AND Operator to understand the technique and how it can be
used to solve the above problem without using to the function technique.
true && ‘Some Age’;
If we run the above, this will return the value ‘Some Age’. So in Logical And Operator if the first value is true it is not going to
use/return that first value; however, if the second value is also true it will use/return the second value.

False && ‘Some Age’;
If we now run the above, this will return false. So in this instance, where the first value is false, that value is what actually gets
used/returned and ignores the second value ever exists.
Therefore if we check for age and the user is below 18 a boolean (false) is returned and this is ignored by JSX. We can use
this tools and technique to add this conditional rendering in our JSX.
The ternary function is great for when you want to do one of two things, while the Logical And Operator is useful for when
you want a condition to do one thing else you want to do nothing at all.
We can make our Logical And Operator even more complex by checking two things in our first value to equate to true or
false for example we can check if the age exists at all and is above 18 to return our JSX. For example:
{ (user.age && user.age >=18) && 
Age: { user.age } 
 }
We have now explored the very basics of conditional rendering techniques we will use over and over again. Eventually, over
time and lots of practice, we will eventually master all three strategies. However, we should now be confident of being able
to make our JSX expressions more dynamic.

ES6 Aside: Let & const
ES6 introduces let and const variables keywords which are alternatives to the var variable keyword. Is there anything
inherently broken with var? No. The only problem with var is that it can be easily misused creating unnecessarily weird
situations. For example: not only can you reassign a var variable but you can also redefine the variable. This means if
recreate a var variable without knowing that you have created it elsewhere in your code, you are essentially overriding the
original variable value and therefore you will run into hard to debug issues.
var nameVar = ‘John Doe’;
var nameVar = ‘Mike’;
The let and const variables prevents you from reassigning/redefining existing variables.
The let variable allows you to reassign the variable however you cannot redefine the variable (i.e. you cannot redeclare the
same variable. You can however reassign it to another type e.g. a string to a number).
let nameLet = ‘John Doe’;
let nameLet = ‘Mike’;

> Uncaught SyntaxError: Identifier ‘nameLet’ has already been declared at…

The const variable does not allow you to reassign nor redefine the variable again.
const nameConst = ‘Frank’;
const nameConst = ‘Barry’;

> Uncaught SyntaxError: Identifier ‘nameLet’ has already been declared at…

nameConst = ‘Barry’;

> Uncaught TypeError: Assignment to content variable at…

By default you should always use the const variable when creating a new variable, however, if you need to reassign the
variable then you should switch to the let variable instead. You should stop using the var variable.
There are a few other differences between var, let and const variables i.e. the scoping of the variables are also different.
The var, let and const variable are all function—scoped meaning that the variable within the function cannot be accessed
outside the function.
function getName(){
name = ‘Paul’;
}
getName();
console.log(name);

> Uncaught ReferenceError: name is not defined at…

Note: we could create the variable called name outside the function and set the value to the function which will work.
The let and const variables are all block-scoped whereas var is not. Bock Scoping is where the variable are also bound to the
code block (e.g. the code block for an if statement or a code block for a for loop). For example: if we had a variable in an if
statement this variable can be accessible outside this code block provided this variable uses var instead of let and const.
const fullName = ‘John Doe’;
If(fullName) {
const firstName = fullName.split(‘ ‘);
}
console.log(firstName)

> Uncaught ReferenceError: name is not defined at…

Remember the rule: ‘const first; if we need to reassign, let; … var never!’

ES6 Aside: Arrow Functions
Arrow functions is a new ES6 syntax and is used heavily throughout React, therefore, it is important to have a basic grasp of
how arrow functions operate.
We are going to compare and contrast a regular ES2015 function with a ES6 Function. The function we are going to create
will square a number.
ES2015 Regular Function Syntax:
const square = function(x) {
return x * x;
};
console.log(square(5));
ES6 Arrow Function Syntax:
const square = (x) => {
return x * x
};
Arrow functions do not need the function keyword. We start with the function argument(s) followed by an arrow and then the
function body.

Arrow functions are always anonymous (unlike ES2015 functions where we can give the function a name). To give an arrow
function a name we must always declare a const or let variable first and assign the arrow function to it as we did above.
Example of ES2015 Function with a Name:
function square (x) {
return x* x;
};
console.log(square(5));
If an arrow function body returns only a single expression we can use the new syntax. We no longer require the curly
brackets. The expression is implicitly returned and therefore we do not need to write the return keyword (compared to the
ES2015 syntax where we need to explicitly return):
const square = (x) => x * x



File Type                       : PDF
File Type Extension             : pdf
MIME Type                       : application/pdf
Linearized                      : No
Page Count                      : 20
PDF Version                     : 1.4
Title                           : Beginners Guide to React
Producer                        : Mac OS X 10.13.6 Quartz PDFContext
Creator                         : Pages
Create Date                     : 2018:10:15 21:46:19Z
Modify Date                     : 2018:10:15 21:46:19Z