JS Practice — Built-in Objects

String.prototype.concat() — returns a new string

📖 Usage Example

const str = 'Hello'
str.concat(', ', 'World', '!')   // → 'Hello, World!'
''.concat('a', 'b', 'c')          // → 'abc'

Use concat() to join two or more strings together, returning a new string without modifying the originals.

String.prototype.concat() — Immutability

.concat() never modifies the original string. Strings in JavaScript are immutable.

Challenge: Implement concatAndCheck(a, b) that returns an object { result, originalUnchanged } where result = a.concat(b) and originalUnchanged is true if a is still its original value.

concatAndCheck('foo', 'bar') // → { result: 'foobar', originalUnchanged: true }

💡 Hints (1)

• Strings are immutable in JavaScript. `.concat()` always returns a new value.