为 Promise.all 创建一个 promise 数组

Question

I have an array of file paths, and I want to read all files inside Promise.all, and then perform some tasks.

var files = ["./file1.txt", "./file2.txt"]

Promise.all(files.forEach(file=>{ /* read file content */}))

Answer 1

You want to use Array.map :

var files = ["./file1.txt", "./file2.txt"]

Promise.all(files.map(async file=>{ /* read file content */}))

If you don't want it to be an async function but want it to return a promise, that's fine too

var files = ["./file1.txt", "./file2.txt"]

Promise.all(files.map(file=>{ /* read file content, return a promise */}))

[edit] here's an example using my preferred file interface, fse - its' just fs but with promises:

var files = ["./file1.txt", "./file2.txt"]

Promise.all(files.map(file=>{ 
    return fse.readFile(file, 'utf-8');
})).then(results => {
    // results is an array of strings of the contents of each file
})

https://www.npmjs.com/package/fs-extra