How Does `Promise.all` Handle Promise Execution: Parallel or Sequential?

Are Node.js Native Promises Processed in Parallel or Sequentially with Promise.all?

Q1: Is Promise.all(iterable) designed to process all promises sequentially or concurrently?

Answer: Promise.all does not execute promises but rather waits for their completion. It does not enforce an execution order or influence whether computations occur in parallel.

Q2: If Promise.all processes promises in parallel, is there a native ES6 mechanism to run them sequentially?

Answer: While Promise.all does not inherently run promises in parallel, if the need arises to execute a sequence of asynchronous functions sequentially, you can use Array::reduce to achieve this:

<code class="js">iterable.reduce((p, fn) => p.then(fn), Promise.resolve())</code>

This transformation converts an array of functions into a chain of sequential promises, where the result of each function becomes the input for the next.

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