Common JavaScript runtime errors, async pitfalls, and browser/Node.js-specific issues.
Attempting to access a property on an undefined or null value.
Accessing a variable that has not been declared in the current scope.
Invalid JavaScript syntax that prevents the script from parsing.
An unhandled rejection from a rejected Promise in async code.
Infinite recursion causes the call stack to overflow.
Calling something as a function when it is not callable.
Browser blocks cross-origin HTTP request missing proper CORS headers.
Attempting to assign a property or mutate an object that is null or undefined.
Declaring a variable with let or const that already exists in the same scope.
Attempting to reassign a value to a variable declared with const.
An asynchronous promise rejected without an attached .catch() or try/catch block.
Attempting to parse a string as JSON using JSON.parse() when the string is actually an HTML page or response.