gistfile1.txt

var assert = require('assert')


// Underscore and/or lo-dash are great
// utility libraries that abstract lots of cruft
// from javascript code. That said,
// there may be times when including a library
// isn't feasible in a project. Let's dig into
// some of the most valuable methods in the project
// and put together our own version.

var _ = {
  //  go over each item is list, running iterator
  each: function(list, iterator, context) {

  },

  //  produce new array from list run through iterator
  map: function(list, iterator, context) {

  },

  //  return a list sorted by iterator
  sortBy: function(list, iterator, context) {

  },

  //  creates function only callable once
  once: function(fn) {
  },

  //  produce a fn only callable once during wait interval (ms)
  throttle: function(fn, wait) {

  }
};



//  tests
var array, fn, createCountFn;


console.log('_.each performs iterator on all input');
array = [];
_.each([1, 2, 3], function(n) {
  array.push(n);
});
assert.deepEqual(array, [1, 2, 3]);



console.log('_.map returns an array of mapped input');
array = _.map([1, 2, 3], function(n) {
  return n + 1;
});
assert.deepEqual(array, [2, 3, 4]);



console.log('_.sortBy sorts by criteria');
array = _.sortBy([{name: 'sally'}, {name : 'bob'}], function(obj) {
  return obj.name;
});
assert.deepEqual(array, [{name : 'bob'}, {name : 'sally'}]);



console.log('_.sortBy does not mutate input');
array = ['b', 'a'];
_.sortBy(array, function(character) {
  return character;
});
assert.deepEqual(array, ['b', 'a']);



// Next three tests use createCountFn

createCountFn = function(count) {
  return function() {
    count++;
    return count;
  }
};


console.log('_.once produces a function only callable once');
fn = _.once(createCountFn(0));
fn();
assert.equal(fn(), 1);



console.log('_.throttle calls only once per given amount of milliseconds')
fn = _.throttle(createCountFn(0), 50);
fn();
assert.equal(fn(), 1);



console.log('_.throttle calls again if you wait until its throttling limit is up');
fn = _.throttle(createCountFn(0), 50);
fn();
setTimeout(function() {
  assert.equal(fn(), 2)
}, 100)


console.log('ALL TESTS PASS');

//  Improvements: test context; _.each for objects{}