JS Template File

Table of Contents

(click to expand/hide)

1. NodeJS Functions
2. JQuery Functions
3. ReactJS Functions
4. JS Functions

NodeJS Functions

included libraries : express, body-parser, ejs, lodash, mongoose, dotenv

include request methods: get, post, listen

---

Initial project creation

1. create a folder, and switch to the folder directory

     mkdir <folder name>

     cd <folder name>

2. create required files (in the folder)

     touch app.js

     mkdir views

     cd views

     touch home.ejs header.ejs footer.ejs

3. initialize npm and install required npm libraries (in the folder)

     npm init

     npm i express body-parser ejs lodash mongoose dotenv

other useful functions

render specific ejs files in nodejs request function

res.render("filename");

res.render("filename", {<var1 in ejs>: <var1 in js>, <var2 in ejs>: <var2 in js>});

• calling variable in ejs

  <%= variablename %>

writing function in ejs file (must use <% and %> to cover every js code)

<% for(let i=0; i<newListItems.length ; i++){ %>
            <div class="item">
                <input type="checkbox">
                <p>
                    <%= newListItems[i] %>
                </p>
            </div>
        <% } %>

calling other ejs file to render in current ejs file

• in this case the header.ejs will render before the div element and footer.ejs will render after the div element

<%- include("header") -%>
<div class="box" id="heading">
   <h1>It's <%= listTitle %>!</h1>
</div>
<%- include("footer") -%>

module.exports

• import Strings/Objects/Functions

  let example = require('path/filename.js');

• export functions

  module.exports.<function name> = function() {
   ... code ...
   return variable/object;
  };

• export functions in bulk

  function example1(){
  }
  function example2(){
  }
  module.exports = {
   example1,
   example2
  }

get the value in url

app.get("/posts/:postName", function(req, res){
console.log(req.params.postName);
});

find one of the key-value in a object array

1. some()
   • return type : boolean value

   if(array.some(item => item.title === req.params.ItemName)){
       console.log("Match Found");
   }

2. find()
   • return type : object

   let foundItem = array.find(item => item.title === req.params.ItemName);
   if(foundItem){
       console.log(foundItem.title);
   }

use .env to hide private information(ex. API key)

1. install dotenv package if have bot install already, and create a .env file

      npm i dotenv

      touch .env

2. Store private information in .env

     API_KEY = 00000000000

3. Calling private information in javascript file

     require("dotenv").config();

     let example = process.env.API_KEY;

using https get request

    const https = require("https"); //make sure to include library, it is a built-in nodejs library so we don't have to npm install it.
    const exampleAPI_URL = "https://api.exampleapi.com/key?=value";
    https.get(exampleAPI_URL, function(res){
        console.log(res.statusCode); //get the status code
        res.on("data", function(data){
            const weatherData = JSON.parse(data); // JSON.parse will convert the response data from hex format to json format
            console.log(weatherData);
            //JSON.stringify(weatherData); //this will turn weatherData from object to string
        });
    });

connect to mongo server and call mongo find function

async function getInfoDB() {
  let result;
  try {
    await mongoose.connect("mongodb+srv://" + process.env.MONGO_USERNAME + ":" + process.env.MONGO_PS + "@cluster0.6gezmfg.mongodb.net/<db name>", { useNewURLParser: true });
    result = await <collection name>.find({});
    mongoose.connection.close();
  } catch (err) {
    console.error(err);
    mongoose.connection.close();
  }
  return result;
}

---

JQuery Functions

Import jquery libraries in html

• Include jquery cdn libraris

<script src="https://code.jquery.com/jquery-3.6.0.min.js"></script>

• Include jquery custom js script file

<script src="./<path>/<script file name>.js"></script>

jquery ajax get method

function functionName() {
  // Fetch and process data
  $.ajax({
    url: "/<pathname>",
    method: "GET",
    async:false, //disallow concurrent running
    success: function (data) {
      function2Name(data);
    },
    error: function () {
      console.log("An error occurred accessing stock info data");
        function3Name();
    },
    complete: function () {
      function4Name();
    }
  });

  // Fetch and process data
  $.ajax({
    url: "/<pathname2>",
    method: "GET",
    async:false, //disallow concurrent running
    success: function (data) {
      function5Name(data);
    },
    error: function () {
      console.log("An error occurred accessing stock info data");
        function6Name();
    },
    complete: function () {
      function7Name();
    }
  });
}

$(document).ready(function () {
  setTimeout(functionName, 1000); // 1000 means delay for 1 second then call function "function"
});

---

React Functions

Creating React App

• In bash

    npx create-react-app <app name>

Start development server

• In bash located into the react app directory

    cd <app name>

    npm start

Upgrade React App version

• In bash located into the react app directory

    cd <app name>

    npm install react-scripts@latest

React in JS file

Import react js file in html

<script src="./src/index.js" type="text/jsx"></script>

Import libraries in js file

import React from 'react';
import ReactDOM from 'react-dom/client';

Inject code to an element (ex. div/h1/p)

import React from 'react';
import ReactDOM from 'react-dom/client';

const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
  <h1>
    Hello World
  </h1>
);

Calling js variable in an element (ex. div/h1/p)

import React from "react";

function Footer() {
  const currentYear = new Date().getFullYear();
  return (
    <footer>
      <p>Copyright ⓒ {currentYear}</p>
    </footer>
  );
}

export default Footer;

React function with parameter (React props)

import React from "react";
import ReactDOM from "react-dom";

function Card(props) {
  return (
    <div>
      <h2>{props.name}</h2>
      <img src={props.img} alt="avatar_img" />
      <p>{props.tel}</p>
      <p>{props.email}</p>
    </div>
  );
}

const root = ReactDOM.createRoot(document.getElementById('root'));
root.render(
  <div>
    <h1>My Contacts</h1>
    <Card
      name="Beyonce"
      img="https://blackhistorywall.files.wordpress.com/2010/02/picture-device-independent-bitmap-119.jpg"
      tel="+123 456 789"
      email="[email protected]"
    />
    <Card
      name="Jack Bauer"
      img="https://pbs.twimg.com/profile_images/625247595825246208/X3XLea04_400x400.jpg"
      tel="+7387384587"
      email="[email protected]"
    />
  </div>,
  document.getElementById("root")
);

useState function

• const [state, setState] = useState(initialState);

  import React, { useState } from "react";
  
  function App() {
    const [count, setCount] = useState(0);
  
    function increase() {
      setCount(count + 1);
    }
  
    function decrease() {
      setCount(count - 1);
    }
  
    return (
      <div className="container">
        <h1>{count}</h1>
        <button onClick={decrease}>-</button>
        <button onClick={increase}>+</button>
      </div>
    );
  }
  
  export default App;

Appending element into a state array

  const [inputText, setInputText] = useState("");
  const [items, setItems] = useState([]);

  function handleChange(event) {
    const newValue = event.target.value;
    setInputText(newValue);
  }

  function addItem() {
    setItems(prevItems => {
      return [...prevItems, inputText];
    });
    setInputText("");
  }

Adding link to a react component

1. First install react-router-dom

   npm install react-router-dom

2. In index.js import BrowserRouter

   import React from 'react';
   import ReactDOM from 'react-dom/client';
   import { BrowserRouter } from 'react-router-dom'
   import App from './App';
   
   const root = ReactDOM.createRoot(document.getElementById('root'));
   root.render(
       <BrowserRouter>
         <App />
       </BrowserRouter>
   );

3. Finally add to the desired react component

    import React from 'react';
    import { Link } from 'react-router-dom';
    import './GameCard.css';
    
    const GameCard = (props) => {
      return (
        <Link to='/about' className="game-card">
          <img className="game-card__image" src={props.imageUrl} alt={props.imgTitle} />
          <div className="game-card__details">
            <h2 className="game-card__title">{props.title}</h2>
            <p className="game-card__description">{props.description}</p>
          </div>
        </Link>
      );
    };
    
    export default GameCard;

---

JS Functions

js arrow function

//Map -Create a new array by doing something with each item in an array.
// const newNumbers = numbers.map(function (x) {
//   return x * 2;
// });
// is same as
const newNumbers = numbers.map( x => x * 2);

//Find - find the first item that matches from an array.
// const newNumber = numbers.find(function (num) {
//   return num > 10;
// })
const newNumber = numbers.find(num => num > 10);

js es6 Spread Operator

 const citrus = ["Lime", "Lemon", "Orange"];
 const fruits = ["Apple", ...citrus, "Banana", "Coconut"];

 const fullName = {
   fName: "James",
   lName: "Bond"
 };

 const user = {
   ...fullName,
   id: 1,
   username: "jamesbond007"
 };

 console.log(user);
// console : Object {fName: "James", lName: "Bond", id: 1, username: "jamesbond007"}

js Ternary Operator (It is an Expression)

• Condition ? Do if True : Do if False
• Example : isEmpty === true ? addFunction() : removeFunction()
  • If we want one of the condition to do nothing, simply set it to null or use && operator
    • isEmpty === true ? addFunction() : null
    • isEmpty === true && addFunction()

1. example 1 (In JavaScript)

    function getFee(isMember) {
      return (isMember ? '$2.00' : '$10.00');
    }
    
    console.log(getFee(true));
    // Expected output: "$2.00"
    
    console.log(getFee(false));
    // Expected output: "$10.00"
    
    console.log(getFee(null));
    // Expected output: "$10.00"

2. example 2 (In React JavaScript)

    import React from "react";
    import Login from "./Login";
    
    var isLoggedIn = false;
    
    const currentTime = new Date(2019, 11, 1, 9).getHours();
    console.log(currentTime);
    
    function App() {
      return (
        <div className="container">
          {/*Ternary Operator*/}
          {isLoggedIn ? <h1>Hello</h1> : <Login />}
          {/*AND Operator*/}
          {currentTime > 12 && <h1>Why are you still working?</h1>}
        </div>
      );
    }
    
    export default App;

js map function

1. example 1

   const array1 = [1, 4, 9, 16];
   
   // Pass a function to map
   const map1 = array1.map(x => x * 2);
   
   console.log(map1);
   // Expected output: Array [2, 8, 18, 32]

2. example 2

   // in emojipedia.js
   const emojipedia = [
     {
       id: 1,
       emoji: "💪",
       name: "Tense Biceps",
       meaning:
         "“You can do that!” or “I feel strong!” Arm with tense biceps. Also used in connection with doing sports, e.g. at the gym."
     },
     {
       id: 2,
       emoji: "🙏",
       name: "Person With Folded Hands",
       meaning:
         "Two hands pressed together. Is currently very introverted, saying a prayer, or hoping for enlightenment. Is also used as a “high five” or to say thank you."
     },
     {
       id: 3,
       emoji: "🤣",
       name: "Rolling On The Floor, Laughing",
       meaning:
         "This is funny! A smiley face, rolling on the floor, laughing. The face is laughing boundlessly. The emoji version of “rofl“. Stands for „rolling on the floor, laughing“."
     },
     {
       id: 4,
       emoji: "🤓",
       name: "Nerd Face",
       meaning:
         "Huge glasses, awkward smile and buck teeth. Used humorously or ironically for nerds or to express how smart you are. Stereotype of a nerd; a smart but funny-dressed person with social deficits."
     }
   ];
   
   export default emojipedia;

   // in App.js
   import React from "react";
   import Entry from "./Entry";
   import emojipedia from "../emojipedia";
   
   function createEntry(emojiTerm) {
     return (
       <Entry
         key={emojiTerm.id}
         emoji={emojiTerm.emoji}
         name={emojiTerm.name}
         description={emojiTerm.meaning}
       />
     );
   }
   
   function App() {
     return (
       <div>
         <h1>
           <span>emojipedia</span>
         </h1>
         <dl className="dictionary">{emojipedia.map(createEntry)}</dl>
       </div>
     );
   }
   
   export default App;

js filter function

const words = ['spray', 'limit', 'elite', 'exuberant', 'destruction', 'present'];

const result = words.filter(word => word.length > 6);

console.log(result);
// Expected output: Array ["exuberant", "destruction", "present"]

js reduce function

const array1 = [1, 2, 3, 4];

// 0 + 1 + 2 + 3 + 4
const initialValue = 0;
const sumWithInitial = array1.reduce(
  (accumulator, currentValue) => accumulator + currentValue,
  initialValue
);

console.log(sumWithInitial);
// Expected output: 10

js find function (return the first element that satisfied the condition)

const array1 = [5, 12, 8, 130, 44];

const found = array1.find(element => element > 10);

console.log(found);
// Expected output: 12

js findIndex function (return the first element's index that satisfied the condition)

const array1 = [5, 12, 8, 130, 44];

const isLargeNumber = (element) => element > 13;

console.log(array1.findIndex(isLargeNumber));
// Expected output: 3

js shallow copy & deep copy

const dude = { name: 'jeff', weapons: { main: 'sword', alt: 'bat' } };
const bruh = { ...dude }; // shallow copy, nested objects still maintain reference to their original object
const bruh2 =  JSON.parse(JSON.stringify(dude)); // deep copy method 1, turn object to string then turn it back to json
const bruh3 = structuredClone(dude); // deep copy method 2