omnimap

Omnimap
=======

Map over multiple arrays/object without thinking too much. Callback function follows the general input arguments of Array.prototype.map.

Usage

$3

```javascript
'use strict';
const omnimap = require('omnimap');
const result = omnimap([1,2,3], [4,5,6], function(a, b, idx, arr) {
// idx is the current idx iteration index
return a + b;
});
console.log(result); // [5, 7, 9];
``

You can do three arrays as well. Well, just give it any number of arrays, and it'll map through.
``javascript
'use strict';
const omnimap = require('omnimap');
const result = omnimap([1,2,3], [4,5,6], [7,8,9], function(a, b, c, idx, arr) {
// idx is the current idx iteration index
return a + b + c;
});
console.log(result); // [12, 15, 18];
``

$3

As with all object looping in js, the order of the outcome is not guaranteed.
``javascript
'use strict';
const omnimap = require('omnimap');
const a = { a: 1, b: 2, c: 3 };
const b = { a: 4, b: 5, c: 6 };
const result = omnimap(a, b, function(a, b, key, arr) {
// key is the currently iterating object key
return a + b;
});
console.log(result); // { a: 5, b: 7, c: 9 };
``

For object mapping, we have a convenient tool that converts the result object into a key-less array.
``javascript
console.log(result.toArray()); // [5, 7, 9];
``

$3

If you don't pass a callback function as the last argument, it will return a evaluator which you can call with a callback.

``javascript
'use strict';
const omnimap = require('omnimap');
const map = omnimap([1,2,3], [4,5,6]);
const result = map(function(a, b, idx, arr) {
// idx is the current idx iteration index
return a + b;
});
console.log(result); // [5, 7, 9];
``

The real reason why I made this

Promise.

``javascript
function doSomethingLethal(payload) {
return someLethalPromiseFunc(payload);
}

const omnimap = require('omnimap');
const controllers = [
doSomethingLethal,
doSomethingLethal,
doSomethingLethal,
];
const payloads = [
{ msg: 'Hello' },
{ msg: 'World' },
{ msg: '世界' }
];

const task = omnimap(controllers, payloads, function(controller, payload, idx) {
payload.id = idx;
return controller(payload);
});

Promise.all(task).then(function(results) {
console.log(results);
});
``

Caveats

1. The maximum iteration count is always the length of the first enumerable given. Make sure that the length of following enumerables are less than or equal to the length of the first enumerable. It would fail node.js VM (undefined reference errors).
2. Object mapping returns its own instance, OmnimapObject, rather than a plain object. This is to hide .toArray() method behind the prototype. However, it still is compatible with all Object.prototype methods.
3. Because of the Caveat#2, testing methods such as chai.assert.deepEqual` would fail. You will have to iterate over each key manually, and assert each member individually.