Implement a function `pipe()` that takes several functions as arguments and returns a new function that will pass its argument to the first function, then pass the result to the second, then pass the result of the second to the third, and so on, finally returning the output of the last function. In other words, calling `pipe(foo, bar, baz)(1, 2,…

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#rangle-pipe

Implement a function pipe() that takes several functions as arguments and returns a new function that will pass its argument to the first function, then pass the result to the second, then pass the result of the second to the third, and so on, finally returning the output of the last function. In other words, calling pipe(foo, bar, baz)(1, 2, 3) would be equivalent to calling baz(bar(foo(1,2,3))).

$ nvm use
$ npm install
$ npm test

index.js

"use strict";

module.exports = function() {
  let fns = arguments;
  return function() {
    let out = arguments;
    for (let fn of fns) {
      if (typeof fn != 'function') throw 'pipe() accepts only functions as arguments';
      out = [ fn.apply(null, out) ];
    }
    return out[0];
  };
};

package.json

{
  "name": "rangle-pipe",
  "version": "1.0.0",
  "author": "Radek Stepan <[email protected]>",
  "main": "index.js",
  "devDependencies": {
    "chai": "^3.5.0",
    "mocha": "^2.4.5"
  },
  "scripts": {
    "test": "./node_modules/.bin/mocha test.js --ui exports --bail --reporter spec"
  }
}

test.js

"use strict";

let assert = require('chai').assert;

let lib = require('./index.js');

exports.foobarbaz = (done) => {
  let foo = (x) => x + 'foo';
  let bar = (x) => x + 'bar';
  let baz = (x) => x + 'baz';

  assert.deepEqual('foobarbaz', lib(foo, bar, baz)(''));
  done();
};

exports.pass = (done) => {
  let foo = (a, b, c) => a + b + c;
  let bar = (x) => x + 2;
  let baz = (x) => x + 3;

  assert.deepEqual(baz(bar(foo(1, 2, 3))), lib(foo, bar, baz)(1, 2, 3));
  done();
};

exports.undefined = (done) => {
  let foo = (x) => x;

  assert.isUndefined(lib(foo, foo, foo)());
  done();
};