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How To Do Promise All For Array Of Array Of Promises

Promises are a powerful feature in JavaScript that allow you to work with asynchronous code in a more structured and manageable way. One common scenario you might encounter is dealing with an array of arrays of promises and wanting to wait for all of them to resolve before continuing with your program. In this article, we'll walk through how to use the `Promise.all` method to achieve this.

So, how do we handle an array of arrays of promises? First, let's break down the problem. You have an array that contains several sub-arrays, each of which holds a set of promises. Your goal is to wait for all the promises in each sub-array to resolve and then move on to the next sub-array.

To solve this, we can break it down into two steps. The first step is to use the `map` method to process each sub-array. Within the `map` function, we will use `Promise.all` to wait for all promises in each sub-array to resolve. Once all sub-arrays are resolved, we can move on to the next step.

Here's an example of how you can achieve this:

Javascript

const arrayOfArraysOfPromises = [[promise1, promise2], [promise3, promise4], [promise5, promise6]];

const arrayOfPromises = arrayOfArraysOfPromises.map(async (arrayOfPromises) => {
  return Promise.all(arrayOfPromises);
});

const results = await Promise.all(arrayOfPromises);
console.log(results);

In this code snippet, we define an array of arrays of promises `arrayOfArraysOfPromises`. We then use the `map` method to iterate over each sub-array. Inside the `map` function, we call `Promise.all` on each sub-array to wait for all promises to resolve. This will give us an array of arrays of resolved values.

Finally, we call `Promise.all` again on the resulting array of promises to wait for all sub-arrays to resolve. The `results` variable will then hold an array of arrays of resolved values, which you can further process as needed.

Using this approach, you can efficiently handle an array of arrays of promises in a concise and readable manner. Remember, the key is to leverage the power of `Promise.all` to handle multiple asynchronous operations and ensure that your code executes in the desired order.

I hope this article has helped you understand how to deal with promises in JavaScript, especially when working with complex data structures like arrays of arrays of promises. By applying these techniques, you can make your code more robust and maintainable when dealing with asynchronous operations. Happy coding!

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