merlin-query v0.0.0

Monarch Query

Monarch Query is a query language developed for the (soon to be released) Monarch ORM.

Designed as a standalone package to allow other libraries to share a common query language. It can be used to filter arrays, and check for matches.

Use it with node or in the browser using browserify.

npm install monarch-query

Example

var query = require('monarch-query');

// create a query for fresh apples.
var q = query({
  kind: 'apple',
  sweetness: { $gt: 60, $lt: 90, $sort: [{ kind: 'asc' }] }
});

// our array of fruits.
var fruits = [
  { kind: 'apple', sweetness: 74 },
  { kind: 'bannana', sweetness: 54 },
  { kind: 'mango', sweetness: 81 },
  { kind: 'apple', sweetness: 99 },
  { kind: 'mango', sweetness: 40 },
  { kind: 'apple', sweetness: 44 },
  { kind: 'apple', sweetness: 61 },
  { kind: 'bannana', sweetness: 97 }
];

// filter the fresh apples from the lot.
var freshApples = q.filter(fruits);
freshApples => [
  { kind: 'apple', sweetness: 61 },
  { kind: 'apple', sweetness: 74 }
];

// our a random fruit.
var randomFruit = { kind: 'apple', sweetness: 74 };

// check to see if the fruit matches the query.
var isMatch = q.match(randomFruit);
isMatch => true

Possible Query Properties

Below is an example of the possible fields in a query object.

{
  field: 'value',
  field: /pattern/,
  field: { $in: ['value1', 'value2'] },
  field: { $notIn: ['notvalue1', 'notvalue2'] },
  field: { $not: 'notvalue' },
  field: { $gt: 1 },
  field: { $gt: 'a' },
  field: { $ln: 1 },
  field: { $ln: 'a' },
  field: { $exists: true },
  $fields: ['field1', 'field2'],
  $sort: [{ field1: 'asc' }, { field2: 'desc' }],
  $offset: 0,
  $limit: 10
}

Query

query(Object query) => Query q

Creates a new query. The query can be used to filter an array of objects, or deterime if a single item is a match.

The query itself supports a collection of operators, as well as regex matching.

Note that operators can be used together.

Direct Match

{ field: 'val' }

Will match any object containing the property field with the value 'val'.

Regex

{ field: /pattern/ }

Will match any object containing the property field with a value matching the /pattern/.

Exists

{ field: { $exists: true } }

Will match any object containing the property field regardless of the value.

Less Than

{ field: { $lt: 1 } }

Will match any object containing the property field with a value less than 1. Less than works with strings and numbers.

Greater Than

{ field: { $gt: 1 } }

Will match any object containing the property field with a value greater than 1. Greater than works with strings and numbers.

Not

{ field: { $not: 'val' } }

Will match any object containing the property field with a value not equal to 'val'.

In

{ field: { $in: ['val1', 'val2'] } }

Will match any object containing the property field with a value matching any within the array. In this case 'val1' and 'val2'.

Not In

{ field: { $notIn: ['val1', 'val2'] } }

Will match any object containing the property field with a value not matching any within the array. In this case anything not equal to 'val1' and 'val2'.

Offset

{ $offset: 10 }

Causes .filter to skip the first 10 matches.

Limit

{ $limit: 10 }

Causes .filter to skip the limit the results to 10 matches. Limit will only be applied after offset. Thus if the offset is 10 then matches 11 through 20 will be included in the results.

Fields

{ $fields: ['field1', 'field2'] }

Results will only contain the fields given within the fields array. In this example, the results will only contain the fields 'field1' and 'field2'.

Sort

{ $sort: [{ field1: 'asc' }, { field2: 'desc' }] }

Results will be sorted by the fields given within each sort object. A sort object may only have one key. The key is the field path you wish to sort by and the value is ether 'asc' for assending or 'desc' for decending. Sorting is done in order of the sort array. In this example, the results will be sorted first by field1 in ascending order, then by 'field2' in decending order.

Match

q.match(Object data) => Boolean isMatch;

Checks an object against the query. For controlling the results see $offset, $limit, $fields, and $sort above.

Filter

q.filter(Array dataSet) => Array matches;

Checks each item in a data set against the query. Returns an array containing the matching items.