JS: String.prototype.indexOf

str.indexOf(search_str)

• Return the start index of first occurrence of search_str.
• Return -1 if not found.

// return index where first b occurs
console.log("abcabc".indexOf("b") === 1);

// example of not found, returns -1
console.log("abcabc".indexOf("xy") === -1);

console.log("ab".indexOf("b") );
// 1

// warning , if you have emoji in string
console.log("🌞b".indexOf("b") );
// 2

str.indexOf(search_str, start_search_pos)

Start search at start_search_pos.

// start at index 1 (including index 1)
console.log("abcabc".indexOf("b", 1) === 1);

// start at index 2
console.log("abcabc".indexOf("b", 2) === 4);

// more than 1 char
console.log("abcabc".indexOf("bc", 2) === 4);