/ Declare a variable
let x;
// Assign a value to a variable
x = 5;
// Declare a variable and assign a value at the same time
let y = 10;
// Declare a constant
const PI = 3.14;
// Data types
let str = 'hello'; // string
let num = 42; // number
let bool = true; // boolean
let obj = {key: 'value'}; // object
let arr = [1, 2, 3]; // array
let func = function() {}; // function
// If statement
if (x > 10) {
console.log('x is greater than 10');
} else {
console.log('x is not greater than 10');
}
// For loop
for (let i = 0; i < 10; i++) {
console.log(i);
}
// While loop
let j = 0;
while (j < 10) {
console.log(j);
j++;
}
// Do while loop
let k = 0;
do {
console.log(k);
k++;
} while (k < 10);
// Functions
function sayHello(name) {
console.log(`Hello, ${name}!`);
}
sayHello('John');
// Arrow functions
let add = (x, y) => {
return x + y;
};
console.log(add(5, 10));
// Objects
let person = {
name: 'John',
age: 30,
sayHello: function() {
console.log(`Hello, my name is ${this.name}`);
}
};
console.log(person.name);
person.sayHello();
// Array methods
let numbers = [1, 2, 3, 4, 5];
// forEach
numbers.forEach(function(num) {
console.log(num);
});
// map
let doubled = numbers.map(function(num) {
return num * 2;
});
console.log(doubled);
// filter
let evens = numbers.filter(function(num) {
return num % 2 === 0;
});
console.log(evens);
// reduce
let sum = numbers.reduce(function(total, num) {
return total + num;
}, 0);
console.log(sum);
