Operacje CRUD na tablicach i iteracja; podstawy obiektów i dostęp do właściwości

Wprowadzenie

Podstawy CRUD tablic

// Make an array
const colors = ["red", "green"];

// Add to end
colors.push("blue");

// Add to start
colors.unshift("pink");

// Remove from end
const last = colors.pop();

// Remove from start
const first = colors.shift();

console.log("Colors now:", colors);
console.log("Removed:", first, last);

Indeks i length

// Read by index and use length
const nums = [10, 20, 30];

console.log("First:", nums[0]);
console.log("Last:", nums[nums.length - 1]);
console.log("Count:", nums.length);

Iterowanie po tablicy

// Iterate values with for…of
const fruits = ["apple", "banana", "cherry"];

for (const value of fruits) {
  console.log("of:", value);
}

// Or use forEach with a small callback
fruits.forEach(function (v) {
  console.log("each:", v);
});

Literały obiektów i dostęp

// Create an object with properties
const user = {
  name: "Ayla",
  level: 1,
  active: true
};

// Dot access
console.log("Name:", user.name);

// Bracket access (useful for dynamic keys)
const key = "level";
console.log("Level:", user[key]);

Łańcuchowanie opcjonalne i spread

// Optional chaining: safely read nested values
const profile = { contact: { email: "ayla@example.com" } };
console.log("Email:", profile.contact?.email);
console.log("Twitter:", profile.social?.twitter);

// Clone and merge with spread
const base = { a: 1, b: 2 };
const extra = { b: 9, c: 3 };

const clone = { ...base };
const merged = { ...base, ...extra };

console.log("Clone:", clone);
console.log("Merged:", merged);

Quiz: metody tablic

Podsumowanie