A utility to generate pivot tables from an array of objects:

var pivot = require('fulcrum');

var data = [{
	name: 'John',
	coin: '5ct',
	number: 30
},{
	name: 'John',
	coin: '5ct',
	number: 2
},{
	name: 'John',
	coin: '10ct',
	number: 3
},{
	name: 'Jane',
	coin: '10ct',
	number: 15
},{
	name: 'Jane',
	coin: '5ct',
	number: 6
}];

In this data model, John has 32 5ct and 3 10ct coins, Jane has 6 5ct and 15 10ct coins.

var res = pivot(data,'name','coin',pivot.sum('number'));

[{
    "name": "John",
    "5ct": 32,
    "10ct": 3
},{
    "name": "Jane",
    "5ct": 6,
    "10ct": 15
}]

pivot(array,rows,cols,reducer);

• array: an array of objects

• rows: a string for the field for rows

• cols: a string for the field for columns

• reducer (optional): an object describing how to calculate the cell value from the matched objects:

    {
    	callback: Function,
    	initialValue: Object
    }
  

  These are the same arguments as passed into Array.reduce: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce.

  If the reducer is omitted, an array of objects is returned in the cell

• pivot.sum(field): return the sum of the values in field field
• pivot.count(): return the number of objects in the cell
• pivot.average(field): return the average
• pivot.min(field): return the minimum
• pivot.max(field): return the maximum

For all these reducers, when no objects are present in the cell, null is returned, except for count()

If you wish, you can attach a convenience method to Array.prototype:

var pivot = require('fulcrum').attach();
var res = data.pivot('name','coin',pivot.sum('number'));

It can also be detached:

pivot.detach();