"Cannot read properties of undefined (reading 'X')" in JavaScript — What It Means and How to Fix It

"Cannot read properties of undefined (reading 'X')" is occurs when code tries to access a property on a value that is undefined.

Key points

• Check the browser console's stack trace to find exactly which line and call triggered the error

Example

let obj;
obj.name  // TypeError: Cannot read properties of undefined (reading 'name')