Small convenience function for chaining functions that utilizes error-first callbacks

chain-callbacks.js

// **************************************************
//  Lib code
// **************************************************
function chainer(errHandler, functions) {
    // Copy functions array so rChainer doesn't modify the referenced array
    return (...input) => rChainer(errHandler, [...functions], ...input);
}

function rChainer(errHandler, functions, ...input) {
    let func = functions.shift();;
    if(func) func(...input, (err, ...val) => {
        if(err) return errHandler(err);
        else rChainer(errHandler, functions, ...val);
    });
}

// **************************************************
//  Example functions
// **************************************************
function causesError() {
    return Math.random() > 0.9 ? true : false;
}

function first(a, callback) {
    if(causesError(a)) return callback("Error from first");
    console.log(a);
    callback(null, a+1, a+2);
};

function second(a, b, callback) {
    if(causesError(a) || causesError(b)) return callback("Error from second")
    console.log(a, b);
    callback(null, b+1, b+2, b+3);
}

function third(a, b, c, callback) {
    if(causesError(a) || causesError(b) || causesError(c)) return callback("Error from third")
    console.log(a, b, c);
}

// **************************************************
//  Usage
// **************************************************
let chain = chainer(
    err => console.log('Error:', err), 
    [first, second, third]
);

for(let i = 0; i < 20; i++) {
    chain(i);
    console.log('----------------------------------')
}