JS Practice — Built-in Objects

String.prototype.indexOf() — found returns index

📖 Usage Example

const str = 'hello world'
str.indexOf('world')    // → 6
str.indexOf('xyz')      // → -1
str.indexOf('l')        // → 2

Use indexOf() to find the index of the first occurrence of a substring, returning -1 if not found.

String.prototype.indexOf()

str.indexOf(searchValue) returns the index of the first occurrence of searchValue, or -1 if not found.

Challenge: Implement findFirst(str, sub) that returns the index of sub in str.

findFirst('hello world', 'world') // → 6
findFirst('hello', 'xyz')         // → -1

💡 Hints (1)