includes() & indexOf() in JavaScript
From the JavaScript Array Methods cheat sheet · Searching & Testing · verified Jul 2026
includes() & indexOf()
Check if array contains a value or find its position
javascript
// Check if array contains value
[1, 2, 3].includes(2); // true
['a', 'b'].includes('c'); // false
// Find index of value
[1, 2, 3].indexOf(2); // 1
['a', 'b'].indexOf('c'); // -1
// Starting from index
arr.includes(value, fromIndex);
arr.indexOf(value, fromIndex);🟢 Essential - Simple value checking
💡 includes() returns boolean, indexOf() returns position
⚡ Use includes() for existence check (cleaner)
⚠️ Uses strict equality (===) for comparison
📌 indexOf() returns -1 if not found