Functional Programming in JavaScript Chapter 01 - run function

ch01-magic-run.js

/*
 * Functional Programming in JavaScript
 * Chapter 01
 * Magical -run- function in support of Listing 1.1
 * Author: Luis Atencio
 */
// -run- with two functions 
var run2 = function(f, g) {
    return function(x) {
        return f(g(x));
    };
};

// -run- with three functions
var run3 = function(f, g, h) {
    return function(x) {
          return f(g(h(x))); 
    };
};

// Test this magical function
var add1 = function(x) {return x + 1;};
var mult2 = function(x) {return x * 2;};
var square = function(x) {return x * x;};
var negate = function(x) {return -x;};

var double = run2(add1, add1);
console.log(double(2)); //-> 4

var testRun = run3(negate, square, mult2);
console.log(testRun(2)); //->-16

Just for completion of my rant above, here is my solution with reversed arguments:

const compose = (...fns) => x => fns.reduceRight((acc, fn) => fn(acc), x);

var echoDocument = document.writeln.bind(document);

var h1 = function (text) { 
    return "<h1>" + text + "</h1>"; 
}

var printMessage = compose(echoDocument, h1);
printMessage("Hello World");

When I first time saw this, I was also very confused as @anhilde mentioned:

var printMessage = run(addToDom('msg'), h1, echo); printMessage('Hello World');

After trying several times, here is my solution:

function addToDom(elementId) { return function(content) { document.querySelector(#${elementId}).innerHTML = content } }

function h1(message) { return '<h1>' + message + '</h1>' }

function echo(message) { return message }

var run = function(f, g, h) { return function(x) { return f(g(h(x))) } }

var printMessage = run(addToDom('msg'), h1, echo) printMessage('Hello World')

emmm...where is run-func details

emmm...where is run-func details

Scroll up the mouse wheel 5 times, it's right there, lol

JavaScript functional programming chapter one. Examples, run(console.log, repeat(3),h2, echo). I can't think solutions, maybe, there are good idea?

And since run is just an alias for compose, you can also use this:

function compose = ( ...fns ) => fns.reduce( ( f, g ) => ( ...args ) => f( g( ...args ) ) );

Usage: compose(fn3, fn2, fn1);

this run can't not do anying?

And since run is just an alias for compose, you can also use this:

function compose = ( ...fns ) => fns.reduce( ( f, g ) => ( ...args ) => f( g( ...args ) ) );

Usage: compose(fn3, fn2, fn1);

maybe this

const compose =  ( ...fns ) => fns.reduce( ( f, g ) => ( ...args ) => f( g( ...args ) ) );

In Listing 1.4, the curry is not given, So I found this code below

const curry = function(f) {
    const var_num = f.length
    return function(...args) {
      if (args.length >= var_num) {
        return f.apply(null, args)
      }
      return function(...new_args) {
        return f.apply(null, args.concat(new_args))
      }
    }
  }

Hope I can help someone who is a beginner like me, good luck!