radytrainer/basic-programming-note

Basic Programming note

A. JavaScript (JS)

#1. Variable

// For global variables
var age = 10;
var isValid = true;
var studentName = "Rady"

// For block scope variables
let age = 18;
let isValid = true;
let studentName = "Rady"

// For block scope variables with cannot be reassigned
const SCHOOL_NAME = "PNC";
const PI = 3.14;

2. Conditional (block)

// IF condition
if (condition) {
    // your code here (work when condition is true)
}

// Example
let age = 18;
if (age == 18) {
    console.log("You are young");
}

// IF-ELSE condition
if (condition) {
    // your code here (work when condition is true)
} else {
    // your code here (work when if condition is false)
}

// Example
let age = 18;
if (age > 18) {
    console.log("You are young");
} else {
    console.log("You are old")
}

// IF-IF condition (work both when condition is true)
if (condition) {
    // your code here (work when condition is true)
} 
if (condition) {
    // your code here (work when condition is true)
}

// Example
let age = 18;
if (age < 18) {
    console.log("You are young");
} 
if (age > 18){
    console.log("You are old")
}

// IF-ELSE IF  condition (work only 1 when condition is true)
if (condition) {
    // your code here (work when condition is true)
} else if (condition) {
    // your code here (work when condition is true)
}

// Example
let age = 18;
if (age > 18) {
    console.log("You are young");
} else if (age < 18) {
    console.log("You are old")
}

// IF-ELSE IF - ELSE condition (work only 1 when condition is true)
if (condition) {
    // your code here (work when condition is true)
} else if (condition) {
    // your code here (work when condition is true)
} else {
    // your code here (work when all condition is false)
}

// Example
let age = 18;
if (age < 18) {
    console.log("You are young");
} else if (age > 18) {
    console.log("You are old")
} else {
    console.log("You are adult")
}

// Conditional (ternary) operator

condition ? expressTrueBlock : expressFalseBlock

// Example
let age = 18;
age < 18 ? console.log("You are young") : console.log("You are old");

#3 Loop (block)

// For loop 
for (expression 1; expression 2; expression 3) {
  // code block to be executed
}

// Example
let arr = [1, 2, 3];
for (let i = 0; i < arr.length; i++) {
    console.log(arr[i]);
}

// For In loop (by index)
for (key in object) {
  // code block to be executed
}

// Example
let arr = [1, 2, 3];
for (let index in arr) {
    console.log(arr[index]);
}

// For Of Loop (by value)
for (variable of iterable) {
  // code block to be executed
}

// Example
let arr = [1, 2, 3]
for (let number of arr) {
    console.log(number);
}

// While Loop 
while (condition) {
  // code block to be executed
}

// Example
let arr = [1, 2, 3]
let i = 0;
while (i < arr.length) {
    console.log(arr[i]);
    i++;
}