export const sequence = function sequence (tasks, fn) {

return tasks.reduce(

(promise, task) => promise.then(() => fn(task)),

Promise.resolve()

)

}

export const parallel = function parallel (tasks, fn) {

return Promise.all(tasks.map(fn))

}

export const chainFn = function chainFn (base, fn) {

if (typeof fn !== 'function') {

return base

}

return function (...args) {

if (typeof base !== 'function') {

return fn.apply(this, args)

}

let baseResult = base.apply(this, args)

// Allow function to mutate the first argument instead of returning the result

if (baseResult === undefined) {

[baseResult] = args

}

const fnResult = fn.call(

this,

baseResult,

...Array.prototype.slice.call(args, 1)

)

// Return mutated argument if no result was returned

if (fnResult === undefined) {

return baseResult

}

return fnResult

}

}