How Can I Sequentially Resolve Promises for File Reading?

How to Sequence Promise Resolutions

Problem:

Consider the code below that serially reads an array of files.

var readFile = function(file) {...};
var readFiles = function(files) {...};

While this recursive solution works, a simpler method is desired without using the readSequential function.

Solution 1: Promise.all

Originally, Promise.all was attempted, but it concurrently invoked all readFile calls.

var readFiles = function(files) {...};

Solution 2: Async Functions

If supported by the environment, an async function can be used.

async function readFiles(files) {...};

Solution 3: Async Generator

For deferred reading, an async generator can be used.

async function* readFiles(files) {...};

Solution 4: For Loop

A simple for loop can be used instead.

var readFiles = function(files) {...};

Solution 5: Reduce

Alternatively, a compact solution using reduce is possible.

var readFiles = function(files) {...};

Solution 6: Promise Libraries

Promise libraries like Bluebird offer utility methods for this purpose.

var Promise = require("bluebird");
var readFileAll = Promise.resolve(files).map(fs.readFileAsync,{concurrency: 1 });

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