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    fantasy-lenses

    0.1.1 • Public • Published

    Fantasy Lenses

    Lenses are composable, immutable getters and setters. Composable in that they allow updating of nested data structures. Immutable in that the setters return copies of the whole data structure.

    Examples

    Nested updating

    var person = {
            name: "Brian McKenna",
            location: {
                number: 1006,
                street: "Pearl St",
                postcode: 80302
            }
        },
        objectLens = require('fantasy-lenses').Lens.objectLens,
        locationLens = objectLens('location'),
        numberLens = objectLens('number'),
        store = locationLens.andThen(numberLens).run(person);
     
    console.log(store.get());
    // 1006
     
    console.log(store.set(1007));
    // { name: 'Brian McKenna',
    //   location: { number: 1007, street: 'Pearl St', postcode: 80302 } }

    Accessing optional fields

    var data = [{
            name: "First record",
            config: {
                type: 2
            }
        }, {
            description: "Hello world",
            config: {
                type: 3
            }
        }, {
            name: "Third record"
        }],
        objectLens = require('fantasy-lenses').PartialLens.objectLens,
        configLens = objectLens('config'),
        typeLens = objectLens('type'),
        configTypeLens = configLens.andThen(typeLens);
     
    console.log(data.filter(function(o) {
        return configTypeLens.run(o).fold(
            function(store) {
                // Get the field's content
                return store.get() == 2;
            },
            function() {
                // Didn't find field
                return false;
            }
        );
    }));
    // [ { name: 'First record', config: { type: 2 } } ]

    Install

    npm i fantasy-lenses

    DownloadsWeekly Downloads

    5

    Version

    0.1.1

    License

    MIT

    Last publish

    Collaborators

    • puffnfresh
    • joneshf