lq - A query like library

lq is a query like library that is inspired by the LINQ library from .NET.

lq instance will attempt to delay the calculation of intermediate values to avoid the time an memory such intermediate values will cost. For example,

var a = [0, 1, 2, 3, 4, 5];
var q = lq(a).where(function (v) { return v % 2 == 0 });
q.each(function (v) { console.info(v) });

will print all the even numbers without producing an array that contains all the even number. In this example, calling .where() returns immediately and the callback function is only invoked when .each() is invoked.

Module

lq(a)

The lq module is a function that returns an query that wraps the array.

Module Functions

lq.of(a)

lq.of() is an alias for lq() and is sometime easier to read.

lq.fieldsOf(o)

fieldsOf() returns a query that contains an array of fields and their values of the for { name: <field-name>, value: <value> }.

lq.join(keySelect, a1 ... an)

Experimental

lq.is(o)

Returns true if o is a lq query, false otherwise.

Query Functions

.count()

Returns the number of values in the query.

.all(predicate)

Returns true if all the predicate returns true for all the values in the query.

.any(predicate)

Returns true if the predicate returns true for any of the values in the query.

.concat(q1, [... qn])

Returns a query that is the concatentaion of one or more queries passed as parameters.

.each(callback)

Calls callback with the values in the query. The callback is callback(value, index) where the value is the value in the query and the index is the position the value would be if toArray() where called on the lq instance.

.first()

Returns the first value in the query.

.forEach()

This is an alias for .each().

.last()

Returns the last value in the query.

.realize()

Ensure that all the selector and predicate functions are invoked. This is used to ensure that expensive work in the selector and predicate functions are not repeated. realize() should be inserted to optimize a query.

.select(selector)

Produce a projection of qyer where all the values in the query is replaced with the result of the selector. The selector might not be called immediately and might be called multiple times on the same value.

.skip(count)

Produce a query that skips at least the count values. If the query has fewer than count values then the query is empty.

.take(count)

Produce a query that contains at most the first count values.

.toArray()

Produce a fresh array that contains the values included in query.

.toObject(keySelector)

Produces an object with the properties with the values of the query and the with the name returned by keySelector(value).

.where(predicate)

Returns a query that only contains values where predicate returns true. predicate is called as predicate(value) where the value is the value in the query.

chuckjaz / lq Goto Github PK

lq's Introduction