What You Need to Know About JavaScript

JavaScript actions, unlike what you’re undoubtedly used to, don’t really stop a program/ function from executing until they’re finished. Instead, it will run in the background while the remainder of the code is executed. The main objective of a callback function in JavaScript is to run code in response to an event. Events like typing or mouse clicks may or may not have been initiated by the user. You may tell your application to run this code every time the user taps a key on the keyboard or clicks an area on the screen by using a callback function. A function provided as an argument to another function is known as a callback function.The order in which JavaScript functions are called determines how they are executed, not the order that they are listed. When a function can call another function and the second (or another) function has been completed, a callback function may execute.
A callback function example:

1
2
3
4
5
6
7
8
9
10
11
function view(x) {
  document.getElementById("demo")
    .innerHTML = x;
}

function Calc(number1, number2, CallbackF) {
  let sum = number1 + number2;
  CallbackF(sum);
}

Calc(2, 9, view);

From the code snippet above, the calc function is called with a callback (CallbackF), and the calc function runs the callback after the calculation is finished. Function view is passed to function calc as an argument.
Asynchronous functions—functions that must wait for one another are where callbacks truly excel. The term “asynchronous” refers to functions that execute concurrently. An example of a callback with asynchronous functions:

1
2
3
4
5
6
setTimeout(CallbackF, 8000);

function CallbackF() {
  document.getElementById("demo")
    .innerHTML = "Topcoder Thrive";
}

CallbackF is passed to setTimeout() as an argument.
You can also pass whole function as an argument to another function as seen below:

1
2
3
4
5
6
7
8
setTimeout(function () {
  CallbackF("Topcoder Thrive");
}, 8000);

function CallbackF(x) {
  document.getElementById("demo")
    .innerHTML = x;
}

function(){ myFunction("Topcoder Thrive"); } is a callback function and is passed to setTimeout() as an argument.

What is a method in Javascript?

A method is a function that belongs to a class or a function that relates to an object or a series of instructions that accomplishes a specific purpose. A function is a set of instructions that accomplishes a certain purpose. An object is anything that has certain attributes and kinds. It is also a property that contains a defined function. There are built-in methods in JavaScript which are predefined bits of code that perform a certain task in a programming framework or language. This simplifies development since programmers do not have to write new methods or functions and can instead utilize the built-in methods in their programs. An example is : toLowercase() of String objects which converts texts to lowercase.
Syntax to write a method in JavaScript:

1
object.method(‘argument’);

An example of a method in JS:

1
2
3
4
5
6
7
8
const text = {
  firsttext: "Hi",
  lasttext: "Bye",
};
text.message = function () {
  return (this.firsttext)
    .toUpperCase();
};

Is JavaScript object-oriented?

JavaScript is a prototype-based object-oriented language, which implies that it doesn’t have classes. Instead, it creates behaviors using a constructor function and then reuses them with the prototype. JavaScript does not have classes, therefore it is not class-based. JavaScript uses an object that serves as a template for obtaining the initial attributes of a new object. Although JavaScript has the term class, it lacks a class statement. It also makes use of cloning rather than inheritance. JavaScript is a highly object-oriented programming language that is ideal for creating object-oriented online applications. JavaScript allows you to create your own objects for use in your own apps. Regarding encapsulation, JavaScript objects are entities that accept data and methods, but they lack advanced native capability for hiding internal information. You can write in events that trigger when you want them to and the code is encased. It may be initiated an infinite number of times. JavaScript objects are unconcerned about their privacy. If no precautions are taken, all properties and methods are publicly available. Also, in JavaScript, we may create different sorts of polymorphism in a variety of ways, and we may have done so unwittingly many times.

Object-oriented programming languages foster creation with a focus on taxonomy and relationships, whereas prototype-based programming languages encourage development with a focus on behavior first and then classifying afterwards.
What is null in JavaScript?
The value null in JavaScript denotes the deliberate exclusion of any object value. It is a primitive value and is considered as false for boolean operations. Null is a datatype in JavaScript.
Checking for null in JavaScript:

1
2
3
4
5
let text = null;

if (text === null) {
  console.log("This text is null");
}

People often mix up undefined with null in JavaScript, but a variable is said to be undefined when it does not exist and is not defined to have any value, while a variable is said to be null if it is defined but has no value.

What is string in JavaScript?

A string is a collection of one or more characters, which can be letters, numbers, or symbols. JavaScript strings are immutable basic data types. Strings are one of the most essential programming concepts to comprehend since they are how we display and deal with text, and language is our primary form of communication and comprehending through computers. A string can be written in JavaScript in three ways: within single quotes (' '), double quotes (" "), or backticks (' '). The type of quotation used on both sides must match, however all three types may be utilized throughout the same script.

Strings with double and single quotations are basically identical. Because there is no standard or official preference for single- or double-quoted strings, the only thing that counts is that they are consistent inside the program. The simplest way to see the output of a string is to use console.log() to display it to the console:

1
console.log("An example of a string.");

Output:
An example of a string.

Assigning/storing a string to a variable:

1
2
3
let exampleString = "An example of a String";
// Outputting it:
console.log(exampleString);

We don’t have to retype a string every time we want to use it by utilizing variables instead, making it easier to deal with and modify strings within our applications.
Concatenating strings: Concatenation is the act of combining two or more strings together to form a new string. To concatenate, we utilize the concatenation operator, which is represented by the + sign. When employed with mathematical operations, the + sign also serves as the addition operator.

For example:

1
2
3
4
"Top" + "coder";

// Outputting it:
// Topcoder.

Concatenation links strings end to end, merging them and producing a whole new string value. If we want a space between the words sea and horse, we must insert a whitespace into one of the strings.

For example:

1
2
3
4
"Top" + " coder";

// Outputting it:
// Top coder

Concatenation is used to link strings and variables holding string values.

For example:

1
2
3
4
5
6
7
let job = "freelancer";
let company = "TopCoder";

let profession = "I am a " + job + " at " + company + ".";

// Outputting it:
// I am a freelancer at Topcoder

Instead of using concatenation, we may enter a variable using the syntax.

__For example: __

1
2
3
4
5
6
let job = "freelancer";
let company = "TopCoder";

let profession = `I am a  {job} at {company} . `;
// Outputting it:
// I am a freelancer at Topcoder.

The strings we write in the source code are enclosed in quotes or backticks, but they are not included in the printed output.
For example:

1
2
3
"Top" + "coder";
// Outputting it:
// Topcoder.

There is a difference between each of these. A string literal is the string exactly as it appears in the source code, including quotation marks. What we observe in the output is a string value that does not include quotation marks. “Top” and “coder” are string literals while Topcoder is a string value. Since quotation marks are used to represent strings, particular considerations must be addressed when utilizing apostrophes and quotes in strings. Attempting to use an apostrophe in the midst of a single-quoted or double-quoted string, for example, will terminate the string, and JavaScript will attempt to read the rest of the intended string as code.
For example:

1
2
3
4
5
6
let wrongstring = 'I'
m a freelancer ';
console.log(brokenString);

// Outputting it:
// unknown: Unexpected token (1:24)

To avoid specific situations of potentially damaged strings like the example above, utilize the opposite string syntax to what you’re now using.

For example:

1
2
3
let string = ' I ”m a freelancer ';
or
let string = “I 'm a freelancer ”;

We may regulate the appearance of quotation marks and apostrophes within our strings by combining single and double quotes. When striving to employ consistent syntax inside project programming files, however, this can be challenging to maintain across a codebase.

To avoid JavaScript from perceiving a quotation as the end of the string we can use the backslash () escape character.

Without risk of breaking the string, the syntax of ’ is for a single quotation, and the syntax of " is for a double quote.

For example:

1
2
3
let string = ' I \’ m a freelancer ';
or
let string = “I\” m a freelancer”;

Both quotes and apostrophes can be used securely with backticks without any extra escaping.

For example:

1
let string = ` I'm a freelancer `;

You may wish to include a newline character or a carriage return into your string at times. To introduce a newline in the output of code, use the \n or \r escape characters.

For example:

1
let longstring = "I am happy to be a part of Topcoder \n and the discord community and \n I am excited to write this article.";

To display the string on numerous lines, we may use the concatenation operator.

For example:

1
2
3
4
5
6
7
8
let longstring = "I am happy to be a part of Topcoder \n” +“
and the discord community and\ n” + “I am excited to write this article.
"; 

// Outputting it:
// I am happy to be a part of Topcoder
// and the discord community
// I am excited to write this article

Instead, we may utilize template backticks to make the code more understandable. On large strings including newlines they avoid the need for concatenation or escaping. Both the string and the newlines will be maintained.

For example:

1
2
3
4
5
6
7
8
let longstring = `I am happy to be a part of Topcoder 
and the discord community and
I am excited to write this article`;

// Outputting it:__
// I am happy to be a part of Topcoder
// and the discord community
// I am excited to write this article.

In order to learn more and get more details about JavaScript, visit: https://www.w3schools.com/js/ or https://www.tutorialspoint.com/javascript/index.htm