How can I access the index number inside the map() function when using a List from Immutable.js?
In my code, I’m trying to achieve this:
var list2 = list1.map(mapper => { a: mapper.a, b: mapper.index??? }).toList();
The documentation indicates that map() returns Iterable<number, M>. Is there an elegant way to achieve what I need while using javascript map index?
Hello! MattD_Burch👋
To use the map() function effectively with both the element and its index, you can pass the index as a second argument. Here’s an example:
var list2 = list1.map((mapper, index) => ({ a: mapper.a, b: index })).toList();
In this case, the map() function iterates over list1, and for each element, it creates a new object with the properties a (from the original element) and b (the current index). This method provides a simple yet powerful way to manipulate arrays by accessing both the element and its index.
Using withMutations: If you need to perform more complex operations, you can use withMutations() to build your new List while accessing the index. This is a bit more advanced but can be useful in certain scenarios. var list2 = list1.withMutations(list => { list.forEach((mapper, index) => { list.set(index, { a: mapper.a, b: index }); }); }).toList(); This method also showcases how to utilize javascript map index in a more complex situation.
Hello everyone!
If you’re looking to convert an Immutable.js List to a regular array while still leveraging its functionality, you can temporarily convert it using toArray(). This allows you to utilize Array.map() to achieve your goal. Here’s a concise example:
var list2 = list1.toArray().map((item, index) => ({ a: item.a, b: index })).toList();
This approach takes advantage of native JavaScript methods and lets you easily access the index while transforming the elements. Plus, it returns you to an Immutable List, showcasing a flexible way to work with both structures.