- Getting Started
- JS in the Web Browser
console.log()- Variables
- Data Types
- String Concatenation
- Operators
- Conditional Statements
This is the method used to output text onto the console (not the screen)
console.log("Hello World!"); //semi-colons are optional
// you can format the code in Console bu using `%c`
console.log("%c Hi There!", "color:blue; font-size:48px;");There are (3) keywords to declare variables:
varthe most lenient type of Variables.letincluded in ES6 somewhat strict type of variablesconstused to create constant (unmodifiable variables)
There are (3) ways to create a variable in JS:
var: creates a somewhat global variable.let: creates a scoped variableconst: creates a CONSTANT variable
/* Using let */
let _var = 67;
function myFunc() {
// this variables is only accessible inside the function.
let _var = 100;
}
/* Using const */
// this variable can not be 'reassigned'
const _constant = "I am unchangeable";
/* Using var */
// This variable can be accessed EVERYWHERE in the code
var _anotherVar = null;Primitive: Data types that are built-in to the language. Examples are:
// nn bb ss u
let _null = null;
let _num = 34;
let _bool = true;
let _bigInt = 456n;
let _string = "ARK";
let _symbol = Symbol("I am a Symbol!");
let _undef = undefined;Non-Primitive: Data Types that are user-defined. Examples are: Objects.
let _myObj = {
name: "ARK",
age: 19,
skinColor: "Dark Orange",
};In the above code an object is assigned to the variable named '_myObj'. The object contains key-value pair this means every properties of object can be accessed by a specific key. There are several ways to access the properties of an object
let name = _myObj.name;
console.log(name);
// output: "ARK"let age = _myObj["age"];
console.log(age);
// Output: 19Concatenation is the process used to combine two or more string together. There are severel ways of concatenating String in JavaScript
- using the
concatmethod - using the
+operator - using the
,operator
Method 1:
str1 = "My";
str2 = "String";
// combines the two existing strings
str3 = str1.concat(str2);
// MyStringMethod 2:
str1 = "My name is";
str2 = "ARK";
console.log(str1 + str2);
// My name isARKMethod 3:
str1 = "My name is";
str2 = "ARK";
console.log(str1, str2);There are many types of loops in JS:
For loop
for (let i = 0; i < 11; i++) {
console.log(i);
}For-in loop:Used for printing the values of an object
// An object literal assigned to a variable named 'Obj'
let obj = {
name: "ARK",
age: 19,
isMale: true,
};
for (let keys in obj) {
console.log(`${keys}: ${obj[keys]}`);
}
/*
Output:
name: ARK
age: 19
isMale: true
*/For-of loop:used to iterate over the elements of an Array
// Array of fruits (string).
let arr = ["lemon", "banana", "apple", "strawberry"];
for (let item of arr) {
console.log(`${item}`);
}
/*
Output:
lemon
banana
apple
strawberry
*/While Loop
let i = 0;
while (true) {
console.log(++i);
}
// Output: 1, 2, 3...let name = "ark";
console.log(name.length); // tells the number of charachters present in the string
console.log(name.toUpperCase()); // converts the string to UPPERCASE
console.log(name.toLowerCase()); // converts the string to lowercase
console.log(name.replace("a", "s")); // replaces 'a' in string 'ark' with 's'. Output: 'srk'A data type that is used to store collection of data types.
let arr = ["banana", 70, 3.142, true];arr.push("ARK"); // adds new element at the end
arr.pop(); // removes element from the end
arr.shift(); // removes element from the front
arr.unshift(); // adds element from the frontSyntax:
condition ? if_true : if_false;Example:
let result = 1 > 2 ? "1 is greater than 2" : "1 is NOT greater than 2";
console.log(result);