The error message "TypeError: iterator1.next is not a function" typically occurs when you are trying to use an iterator object that doesn't have a .next() method. In JavaScript, iterator objects should have a .next() method to be used properly with for...of loops or the next() function.

There are several possible reasons for this error, so let's explore some common scenarios and how to resolve them:

  1. Using a Non-Iterable Object with for...of Loop: If you try to use a for...of loop with an object that is not iterable (i.e., it doesn't have an iterator), this error can occur. Make sure you are using an iterable object (e.g., arrays, strings, sets, maps) in your for...of loop.

Example:

javascript
const obj = { a: 1, b: 2, c: 3 }; // This will result in the error since 'obj' is not iterable for (const item of obj) { console.log(item); }
  1. Using a Non-Iterable Object with the next() Method: Similar to the previous scenario, if you try to call the .next() method on a non-iterable object, you'll encounter this error. Ensure that the object you are working with has a proper iterator.

Example:

javascript
const obj = { a: 1, b: 2, c: 3 }; const iterator = obj[Symbol.iterator](); // This will result in the error since 'obj' is not iterable const result = iterator.next();
  1. Using an Incorrect Iterator: If you manually create an iterator and accidentally use the wrong object as the iterator, it can result in this error. Double-check that you are using the correct iterator object.

Example:

javascript
const iterable = [1, 2, 3]; const iterator = iterable.values(); // Incorrect iterator // This will result in the error since 'iterator' is not the correct iterator for 'iterable' const result = iterator.next();

To resolve this error, ensure that you are using iterable objects (e.g., arrays, strings, sets, maps) and correct iterators (e.g., using iterable[Symbol.iterator]() for arrays) when working with for...of loops or the .next() method. If you encounter this error in a specific context in your code, review the relevant code block and verify that you are using iterators correctly.

Have questions or queries?
Get in Touch