Basics of Javascript I

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I have been learning Javascript to learn front-end development. Below are the steps I took in learning. I actively utilized https://www.learn-js.org/ website.

History of Javascript:

Javascript, often abbreviated as JS, is one of the core technologies of the World Wide Web. Developed by Brandan Eich, a Netscape programmer, Javascript supports event-driven, functional, and imperative programming styles. Javascript is mainly a client-side language ; It runs on a computer within a brower. However, recent introduction of Node.js has allowed Javascript to execute code on servers.

Basics of Javascript I :

1. Variables and Types:

Every variable in Javascript is defined using the ‘var’ keyword.

var myNumber = 3;                   // a number
var myString = "Hello, World!"      // a string
var myBoolean = true;               // a boolean
var myArray = [];                    // an array
var myObject = {};                  // an object
var emptyVariable = null;           // null
var questionMark;                   //undefined
console.log(questionMark);          //prints out undefined

2. Array:

Javascript can hold an array of variables that have different types.

var array = [1, 2, 3, 4];               //example array
var sameArray = new Array(1, 2, 3, 4);  //same array
var diffArray = ["hi", 9, {}].          //array of different types

To address elements in an Array, use indexing.

var array = [1, 2, 3, 4];               
console.log(array[1]);                   //prints out 3
console.log(array[array.length - 1]);    //prints out 4

We can also assign variables to locations where previous cells were undefined.

var array = [];
array[2] = "hi";               
console.log(array);   //prints out [undefined, undefined, "hi"]

3. Array manipulation:

Arrays in Javascript can function as a Stack using ‘push’ and ‘pop’ methods.

var array = [1, 2, 3];
array.push(4);
array.push(5);
console.log(array);   //prints out [1, 2, 3, 4, 5]
array.pop();
console.log(array);   //prints out [1, 2, 3, 4]

Arrays in Javascript can also function as a Queue using ‘shift’ and ‘unshift’ methods.

var array = [1, 2, 3];
console.log(array.shift());    //prints out 1
console.log(array.shift());    //prints out 2
console.log(array);            //prints out [3]
array.unshift(0);
console.log(array);            //prints out [0, 3]

Arrays in Javascript also support splicing, which removes a certain part from an array to create a new array, made up from the part we took out.

var array = [0,1,2,3,4,5,6,7,8,9];
var splice = array.splice(3,5);

console.log(splice);        // prints out [3, 4, 5, 6, 7]
console.log(array);       // prints out [0, 1, 2, 8, 9]

4. Operators:

Addition in Javascript is used for addition and concatenation of strings.

var a = 1;
var b = 2;
var c = a + b;     // c equals 3
var hello = "Hello";
var word = " World";
var full = hello + word; //full equals "Hello World"

Other Mathematical Operations:

var a = 5;
var b = 1;
var c = a - b;    //c equals 4
console.log(a * b);     // prints out 5
console.log(a / c);     // prints out 1.25
console.log(a % b);     // prints out 1

Javascript also has Math module.

• Math.abs calculates the absolute value of a number
• Math.exp calculates e to the power of a number
• Math.pow(x,y) calculates the result of x to the power of y
• Math.floor removes the fraction part from a number
• Math.random() will give a random number x where 0<= x <1

Basics of Javascript I is to be continued in the next article Basics of Javascript II.

Stay Tuned!