JS Recursion

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Sun Jun 30 2024 05:26:31 GMT+0000 (Coordinated Universal Time)

In an earlier project you learned about truthy and falsy values, which are values that evaluate to true or false. In JavaScript, some common falsy values you'll see are null, undefined, the number 0, and empty strings.

Rather than check if a value is equal to a falsy value, you can use the logical NOT operator (!) to check if the value itself is falsy. For example:

const num = 0;

console.log(num === 0); // true
console.log(!num); // true

A good way to check and normalize numbers in JavaScript is to use the built-in parseInt() function, which converts a string into an integer or whole number. parseInt() takes at least one argument, a string to be converted into an integer, and returns either an integer or NaN which stands for Not a Number. For example:

parseInt(2.2); // 2
parseInt("2e+3"); // 2
parseInt("e") // NaN

Next, you need to check if the value returned by the parseInt() function is a number or not.

To do that, you can use the isNaN() function. This function takes in a string or number as an argument, and returns true if it evaluates to NaN. For example:

isNaN("test"); // true
isNaN(2); // false
isNaN("3.5"); // false

The setTimeout function takes two arguments: a callback function and a number representing the time in milliseconds to wait before executing the callback function.

For example, if you wanted to log "Hello, world!" to the console after 3 seconds, you would write:

setTimeout(() => {
  console.log("Hello, world!");
}, 3000);

If you test your code, you'll notice that your console logs are not in the expected order. Instead of logging "free", pausing for a second before logging "Code", and finally logging "Camp", you'll see this:

Example Code
free
Camp
Code
This is because the setTimeout() function is asynchronous, meaning that it doesn't stop the execution of the rest of your code. All the code in the showAnimation() function runs line by line, but because setTimeout() is asynchronous, free and Camp are logged to the console immediately, and then Code is logged to the console after a one second delay.

While asynchronous, or async, code can be difficult to understand at first, it has many advantages. One of the most important is that it allows you to write non-blocking code.

For example, imagine you're baking a cake, and you put the cake in the oven and set a timer. You don't have to sit in front of the oven waiting the entire time – you can wash dishes, read a book, or do anything else while you wait for the timer to go off.

Async code works in a similar way. You can start an async operation and other parts of your code will still work while that operation is running.

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JS Basics JS Fundamentals basic regular expressions, template literals, addEventListener() method string and array methods Date Object, switch, join(), split(), reverse() Modern JS methods localStorage JS JS Recursion Regular Expressions basic algorithmic thinking, bubble, selection, insertion sort advanced array methods. split(), map(), filter(), reduce(), sort(), Math.min(), Math.max(), Math.pow() functional programming object oriented programming intermediate object oriented programming fetch and promise asynchronous programming JS Loops

#html #javascript #nodejs

How to Save HTML Form Data in JSON - Express

<form action="/new" method="post">
 
  <input name="title" type="text">
  <input name="description" type="text">
  <button type="submit">Submit Form</button>
 
</form>

> More steps

#javascript

Get URL and URL Parts in JavaScript

var newURL = window.location.protocol + "//" + window.location.host + "/" + window.location.pathname + window.location.search

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Add event listener to multiple buttons with the same class

    btns = document.getElementsByClassName("saveBtn");
    for (var i = 0; i < btns.length; i++) {
        btns[i].addEventListener("click", function () {
			//Add function here
        });
    }

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Replace Textarea with Codemirror editor

<link rel="stylesheet" type="text/css" href="plugin/codemirror/lib/codemirror.css">

<body>
	<textarea class="codemirror-textarea"></textarea>
</body>

<script>

$(document).ready(function(){
    var codeText = $(".codemirror-textarea")[0];
    var editor = CodeMirror.fromTextArea(codeText, {
        lineNumbers : true
    });
});

</script>

<script type="text/javascript" src="plugin/codemirror/lib/codemirror.js"></script>

#javascript #nodejs #commandline

HTTPS Redirect in Nodejs

npm install heroku-ssl-redirect

> More steps

#javascript #nodejs

Save to MongoDB without Duplicates Using Mongoose

var mongoose = require('mongoose');
var Schema = mongoose.Schema;

const exampleSchema = new Schema({
    title: { type: String , required: true},
    content: [{type: String}]
});


var Example = mongoose.model('Example', exampleSchema);
module.exports = Example;

> More steps

#html #javascript #jsfunctions #dom #dommanipulation

getAttribute() - how to get the value of any attribute of HTML element

<html>

<input id="contact" name="address">

<script>

    var x = document.getElementById("contact").getAttribute('name');

</script>

</html>

#javascript

Full Stack Developer

function full_stack_developer() {
    full_stack_developer();
}

#javascript #javascript #functions #parameters

Required Parameters for Functions in JavaScript

 const isRequired = () => { throw new Error('param is required'); };

const hello = (name = isRequired()) => { console.log(`hello ${name}`) };

// These will throw errors
hello();
hello(undefined);

// These will not
hello(null);
hello('David');
The idea here is that it uses default parameters, like how the b parameter here has a default if you don’t send it anything:
function multiply(a, b = 1) {
  return a * b;
}

#javascript

3 Ways To Detect Selenium Bots Using Javascript - CodingTutz

if (navigator.webdriver) {
    document.body.innerHTML = "This is a Bot";
}

#javascript

Copy Text to Clipboard with Line Breaks

function copyToClipboard(){

    var codeToBeCopied = document.getElementById('code-snippet').innerText;
    var emptyArea = document.createElement('TEXTAREA');
    emptyArea.innerHTML = codeToBeCopied;
    const parentElement = document.getElementById('post-title');
    parentElement.appendChild(emptyArea);

    emptyArea.select();
    document.execCommand('copy');

    parentElement.removeChild(emptyArea);
    M.toast({html: 'Code copied to clipboard'})

    }

#javascript #promises #howto

How to Get the Domain From A URL Using Javascript

var url = "http://scratch99.com/web-development/javascript/";
var urlParts = url.replace('http://','').replace('https://','').split(/[/?#]/);
var domain = urlParts[0];

#javascript

Mapping an Object

const object1 = {
  a: 'somestring',
  b: 42
};

for (let [key, value] of Object.entries(object1)) {
  console.log(`${key}: ${value}`);
}

#javascript #jquery

jQuery.post() - AJAX for post requests

$.ajax({
  type: "POST",
  url: url,
  data: data,
  success: success,
  dataType: dataType
});

#javascript

How to store fetch response in javascript variable - Stack Overflow

async function fun() {
  return fetch('https://jsonplaceholder.typicode.com/todos/1').then(res => res.json());
}

const data  = await fun();

JS Recursion

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