Recursion with node to process on each item from an array

recursion.md

Recursion on array with Promises

Sometime you just want to do operations on a bunch of datas. Oh wait, there is Promises to resolve before.. Here is a simple proposal to solve it.

// Act like it is a database
const users = [
    { name: "ugo", age: 28 },
    { name: "camille", age: 25 }
]



// Fetch users from fake database
function _fetchUsers() {
    return new Promise((res,rej) => {
        console.log('** Fetching users')
        setTimeout(() => {
            console.log('** Found users', users)
            res(users)
        }, 1500);
    })
}



// Do something on users
function processAllUsers() {
    console.log('** Starting the app');
    return _fetchUsers()
        .then(users => waitForEach(user => logName(user), users))
        .catch(e => console.error('Oops:', e))
}

const logName = user => {
    return new Promise((res, rej) => {
        console.log('** The name is: ', user.name)
        res(user.name)
    })
};

/**
 * Recursive call on each element from the passed array
 * @param {function} processFunc 
 * @param {array} array to use
 */
const waitForEach = (processFunc, [head, ...tail]) =>
    !head
        ? Promise.resolve()
        : processFunc(head).then(waitForEach(processFunc, tail))

processAllUsers()