Olio

Look at the Docco for now.

Ascension is a comparator builder. It builds comparators for composite keys. I created it because I find myself writing this function over and over again.

function compare (left, right) {
    var compare = left.lastName < right.lastName
                ? -1 : left.lastName > right.lastName
                     ? 1 : 0
    if (compare != 0) {
        compare = left.lastName < right.lastName
                ? -1 : left.lastName > right.lastName
                     ? 1 : 0
    }
    return compare
}

Not last name first specifically, but that sort of compare these properties and if they're equal, then compare those properties.

What I really don't like about these comparators is having to unit test these functions because they're usually not directly accessible to the code, so I have to expose them for unit testing or else set up and tear down more complicated tests to tickle each branch with different values.

With Ascension the comparator is declarative.

var comparator = ascension([ String, String ], function (object) {
    return [ object.lastName, object.firstName ]
})

Now the comparator only needs to be invoked once in a unit test to get complete coverage.

The first argument is an array with comparator methods for each member of the composite key. The second argument is a method that returns an array that contains the members of the composite key.

Heres an example with a single field key.

var comparator = ascension([ function (left, right) { return left - right } ], function (object) {
    return [ object.createdAt ]
})

The above can be simplified by using Numeric to tell Ascention to use a default numeric comparator.

var comparator = ascension([ Numeric ], function (object) {
    return [ object.createdAt ]
})

You can use both Numeric and String as sigils.