4 important part of JavaScript must read for the beginners

If you are a beginner of JavaScript and have a minimum knowledge about programming language, this article is going to more easy and understandable for you. So lets Start.

JavaScript has a little difference from other programming languages. It has no concept of input or output. Basically, JavaScript’s mechanism is designed to run as a scripting language in host environment(browser). Its syntax and structure is inspired from Java and C.

JavaScript is also known as multi-paradigm and dynamic language. It also contain types, operators, built-in objects, methods like other languages.

Now we can start the 10 important parts of JavaScript.

1. Variable
   In JavaScript, variables are declared as let, const and var.
   Firstly, we will talk about ‘let’ variable. It is used as a block-level variable. that means it is accessible from a block. for example:

// here variable i is initialized as let
//i is not visible out here
for (let i = 0; i < 5; i++) {
  // i is only visible in here
}

// i is not visible out here

Now lets talk about ‘const’. const have come from constant, which means never change.

const K = 8; // you can not change it
k = 1; // here you got an error because you cannot change a constant variable.

Lastly, ‘var’ is the oldest variable type. basically using var you can access it from everywhere.

// here variable i is initialized as var
//i is visible out here
for (let i = 0; i < 5; i++) {
  // i is visible in here
}

// i is visible out here

2. Operator
JavaScript has operators like other language have. +, -, *, / and %.

there are some operator which uses for comparison<, >, <= and >=.In JavaScript there is a simple difference. between == and ===.I will explain with an example:

555 == '555'; // true
0 == false; // true
555 === '555'; // false
0 == false;   // false

3. Strings
Strings in JavaScript are successions of Unicode characters. String is sequences of UTF-16 code units, each unit is represented by a 16-bit number.

There are some built-in method in string like length, charAt, replace, toUpperCase etc. Lets see some example:

'javascript'.length; // 10
'hello'.charAt(0); // "j"
'hello, javascript'.replace('javascript', 'java'); // "hello, java"
'javascript'.toUpperCase(); // "JAVASCRIPT"

4. Number
Numbers in JavaScript follows “Double-precision 64-bit format IEEE 754 values”.

0.1 + 0.2 == 0.30000000000000004;

There are some build in function that give us some interesting output like sin, PI, parseInt, parseFloat, isNaN. Lets have a look some example:

Math.sin(3.5);
parseInt('123', 10); // 123
parseInt('010', 10); // 10
isNaN(NaN); // true

here sin function gives us the value of sin and parseInt function makes a string to binary, octal , decimal or any number system.

these are the important things which are must for the beginners.