What's the difference between splice and slice methods?

const arr = [1, 2, 3, 4, 5];
 
// splice — modifies array
const removed = arr.splice(1, 2); // Removes 2 elements from index 1
console.log(arr);     // [1, 4, 5] — array changed!
console.log(removed); // [2, 3] — removed elements
 
// slice — doesn't modify array
const part = arr.slice(1, 3); // Takes elements from 1 to 3 (excluding 3)
console.log(arr);  // [1, 4, 5] — array unchanged
console.log(part); // [4, 5] — new part

const fruits = ['apple', 'banana', 'orange', 'pear'];
 
// Copy elements from index 1 to 3 (excluding 3)
const copy = fruits.slice(1, 3);
console.log(copy);  // ['banana', 'orange']
 
// Original unchanged!
console.log(fruits); // ['apple', 'banana', 'orange', 'pear']
 
// Can omit second parameter — to end
const rest = fruits.slice(2); // ['orange', 'pear']

const fruits = ['apple', 'banana', 'orange', 'pear'];
 
// Remove 2 elements from index 1
const removed = fruits.splice(1, 2);
console.log(removed); // ['banana', 'orange'] — removed elements
 
// Original changed!
console.log(fruits); // ['apple', 'pear']

const arr = [1, 2, 3, 4];
const copy = arr.slice(1, 3); // Only copies, doesn't add
 
// Can't add elements through slice!

const arr = [1, 2, 3, 4];
 
// Remove 1 element from index 1 and add new ones
arr.splice(1, 1, 'new', 'elements');
console.log(arr); // [1, 'new', 'elements', 3, 4]

// ✅ When you need part of array
const numbers = [1, 2, 3, 4, 5];
const middle = numbers.slice(1, 4); // [2, 3, 4]
 
// ✅ For copying entire array
const copy = numbers.slice(); // [1, 2, 3, 4, 5]

// ✅ When you need to modify array
const items = [1, 2, 3, 4, 5];
items.splice(2, 2); // Remove 2 elements from index 2
console.log(items); // [1, 2, 5]

const arr = [1, 2, 3, 4];
 
// ❌ Mistake — think slice modifies array
const part = arr.slice(1, 3);
console.log(arr); // [1, 2, 3, 4] — unchanged!
 
// ❌ Mistake — think splice doesn't modify array
const removed = arr.splice(1, 2);
console.log(arr); // Changed!

const arr = [1, 2, 3, 4];
 
// ❌ Mistake — don't understand what's returned
const result1 = arr.slice(1, 3);  // Returns [2, 3]
const result2 = arr.splice(1, 2); // Returns [2, 3]
 
// ❌ Mistake — think splice returns new array
// Actually it returns REMOVED elements!