@ambassify/aql-memory-filter

aql-memory-filter

Run AQL conditions agains datasets in memory. This is an implementation of the AQL condition filtering that can be run against an array in memory. You can find database-specific implementations in various Ambassify projects, in the future we hope to be able to provide these implementations here as well.

A list of all operators should be available in the spec.

Usage

npm install --save @ambassify/aql-memory-filter

const aqlFilter = require('@ambassify/aql-memory-filter');

const dataset = [
    { id: 1, type: 'post', title: 'Hello', likes: 5 },
    { id: 2, type: 'post', title: 'World', likes: 10 },
    { id: 3, type: 'article', title: 'This', likes: 32 },
    { id: 4, type: 'post', title: 'Is', likes: 4 },
    { id: 5, type: 'image', title: 'Me', likes: 100 },
];

const condition = {
    operator: 'and',
    value: [
        { key: 'type', operator: 'in', value: [ 'post', 'image' ] },
        { key: 'likes', operator: 'gte', value: 10 },
    ]
};

// filtered array includes ids 2 and 5
const filtered = aqlFilter(dataset, condition);

// test will return `true`
const ok = aqlFilter.test(dataset[1], condition);

// test will return `false`
const notOk = aqlFilter.test(dataset[0], condition);

Value retrieval

It is possible to customize how values are retrieved and the semantics of matching them using the mapTest.

mapTest will receive items from the dataset one by one, the condition, and a callback. mapTest passes all values it finds for the condition to the callback, which will in turn return whether or not the item matches the condition.

The default implementation looks like the code below and will simply retrieve the value at the key property and test it.

function _defaultMapTest(input, condition, cb) {
    return cb(_get(input, condition.key));
}

aqlFilter(dataset, condition, { mapTest: _defaultMapTest });

A different implementation might want to check an array of properties and mandate that at least one matches.

const propertyMapper = (input, condition, cb) => {
    const { key } = condition;

    if (/^prop\./.test(key)) {
        const prop = key.replace(/^prop\./, '');

        return input.properties.reduce((r, p) => {
            if (p.key == prop)
                return r || cb(p.value);
            return r;
        }, false);
    }

    return cb(input[key]);
};

aqlFilter(dataset, condition, { mapTest: propertyMapper });