Javascript: Recursive functions and Promises/A+

rec-func-promise.js

/**
 * Javascript Promises/A+ and recursive functions
 * A simplified example
 * Inspired by: https://kostasbariotis.com/node-js-recursion/
 *
 * Output:
 * 1: async job simulation started
 * 1: job done
 * 2: async job simulation started
 * 2: job done
 * 3: async job simulation started
 * 3: job done
 * all done!
 */
 
rec(1)
.then((res) => {
    console.log(res);
});

function rec(depth) {
    return new Promise((fulfill, reject) => {
        console.log(depth + ': async job simulation started');
        setTimeout(() => {
            console.log(depth + ': job done');
            fulfill(depth);
        }, 1000);
    })
    .then((depth) => {
        if (depth < 3) {
            return rec(depth + 1);
        } else {
            return "all done!";
        }
    })
    .catch((err) => {
        console.log(err);
    });
}