Functional JavaScript: simple function pipeline creators

function-pipeline-creator.js

let pipe = function() {
    let functions = arguments,
        intermediate = undefined;

    return function() {
        intermediate = functions[0].apply(this, arguments);
        for(let i = 1; i < functions.length; i++) {
            intermediate = functions[i](intermediate);
        }

        return intermediate;
    };
};

// Example
let concat = function(a, b) {
        return a + ' ' + b;
    },
    format = function(message) {
        return message.charAt(0).toUpperCase() + message.slice(1).toLowerCase();
    },
    period = function(message) {
        return message.charAt(message.length - 1) !== '.' ? message + '.' : message;
    },
    pipedFunction = pipe(concat, format, period);

let result = pipedFunction('hello world,', 'this message has been piped');
console.log(result); // "Hello world, this message has been piped."

function-pipeline-iterator.js

let pipeI = function() {
    let functions = arguments;

    return function * pipe() {
        let i = 0, intermediate = functions[i++].apply(this, arguments);
        yield intermediate;

        for(; i < functions.length; i++) {
          intermediate = functions[i].call(this, intermediate);
          yield intermediate;
        }
    }
};

// Example
let concat = function(a, b) {
        return a + ' ' + b;
    },
    format = function(message) {
        return message.charAt(0).toUpperCase() + message.slice(1).toLowerCase();
    },
    period = function(message) {
        return message.charAt(message.length - 1) !== '.' ? message + '.' : message;
    },
    pipedFunction = pipeI(concat, format, period);

let iterator = pipedFunction('hello world,', 'this message has been piped iteratively');
console.log(iterator.next().value); // "hello world, this message has been piped iteratively"
console.log(iterator.next().value); // "Hello world, this message has been piped iteratively"
console.log(iterator.next().value); // "Hello world, this message has been piped iteratively."

function-pipeline-promise.js

let pipeP = function() {
    let functions = arguments,
        recursivePromise = function(value, i) {
            return new Promise((resolve, reject) => {
                functions[i](value)
                    .then(function(intermediate) {
                        i += 1;

                        if(i < functions.length) {
                            recursivePromise(intermediate, i).then(resolve, reject);
                        } else {
                            resolve(intermediate);
                        }
                    }, reject);
            });
        };

    return function() {
        let i = 1;
        return new Promise((resolve, reject) => {
            functions[0].apply(this, arguments)
                .then((intermediate) => {
                    recursivePromise(intermediate, i).then(resolve, reject);
                }, reject);
        });
    };
};

// Example
let concat = function(a, b) {
        let v = a + ' ' + b;
        return Promise.resolve(v);
    },
    format = function(message) {
        let v = message.charAt(0).toUpperCase() + message.slice(1).toLowerCase();
        return Promise.resolve(v);
    },
    period = function(message) {
        let v = message.charAt(message.length - 1) !== '.' ? message + '.' : message;
        return Promise.resolve(v);
    },
    pipedFunction = pipeP(concat, format, period);

pipedFunction('hello world,', 'this message has been piped using Promises')
    .then((message) => console.log(message)); // "Hello world, this message has been piped using promises."