Array Pivot

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
}]

API

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

Built in reducers

• 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()

Convenience attachments to Array.prototype

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();