selectorator
selectorator
is an abstraction API for creating selectors via reselect with less boilerplate code.Table of contents
- Shorthand types - TypeScript - deepEqual - isEqual - memoizer - memoizerOptionsInstallation
$ npm i selectorator --save
Versions
Versions ofselectorator
on or above 3.x.x
will use the corresponding major version of reselect
as a dependency. If you wish to still use the 2.x.x
branch of reselect
for your application, then you should continue using the 1.x.x
branch of selectorator
.If you would like to learn more about the breaking changes related to the major version change for
reselect
, please visit the reselect
CHANGELOG.Usage
import createSelector from "selectorator";
// selector created with single method call
const getBarBaz = createSelector(
["foo.bar", "baz"],
(bar, baz) => {
return `${bar} ${baz}`;
}
);
const state = {
foo: {
bar: "bar"
},
baz: "baz"
};
console.log(getBarBaz(state)); // "bar baz"
Not a whole lot of magic here, just simplifying the creation of the "identity selectors" that
reselect
requires, instead replacing them with a standardized dot- or bracket-notation string for retrieval of a nested property in the state object.That said, you can still use your own custom identity selectors, or compose selectors, if you so choose. Here is the example from the
reselect
README modified to use selectorator
:// subtotal built using simple method
const getSubtotal = createSelector(
["shop.items"],
items => {
return items.reduce((sum, { value }) => {
return sum + value;
}, 0);
}
);
// tax builtrued with simple method combined with other selector
const getTax = createSelector(
[getSubtotal, "shop.taxPercent"],
(subtotal, taxPercent) => {
return subtotal * (taxPercent / 100);
}
);
// total build entirely with other selectors
const getTotal = createSelector(
[getSubtotal, getTax],
(subtotal, tax) => {
return {
total: subtotal + tax
};
}
);
const state = {
shop: {
taxPercent: 8,
items: [{ name: "apple", value: 1.2 }, { name: "orange", value: 0.95 }]
}
};
console.log("subtotal: ", getSubtotal(state)); // 2.15
console.log("tax: ", getTax(state)); // 0.172
console.log("total: ", getTotal(state)); // {total: 2.322}
Shorthand types
The following types of shorthand are available for parameter selector creation:- Pulls from state:
string
=> `'foo0.bar'
- number
=> 0
- Array
=> ['foo', 0, 'bar']
- Pulls from specific argument:
Object
=> {path: 'foo[0].bar', argIndex: 1}
Please note that the
Object
usage is the only approach that will allow for selection of parameters. All other shorthands will pull from the first parameter.TypeScript
Selectorator now supports two optional type parameters, it accepts an Input type param (usually the redux state) and the expected output type.When creating a selector that accepts multiple params, the state should be array of the input types example
i.e
createSelector<[State, number[], boolean], string>
import createSelector from "selectorator";
interface State {
foo: {
bar: string;
};
baz: string;
};
// State is input type, string is output type
const getBarBaz = createSelector<State, string>(
["foo.bar", "baz"],
(bar, baz) => {
return `${bar} ${baz}`;
});
// getBarBaz() has type signature: (state: State) => string;
const getBarBaz2 = createSelector<any, string>(
["foo.bar", "baz"],
(bar, baz) => {
return `${bar} ${baz}`;
});
// getBarBaz2() has type signature: (state: any) => string;
const getBarBaz3 = createSelector(
["foo.bar", "baz"],
(bar, baz) => {
return `${bar} ${baz}`;
});
// getBarBaz3() has type signature: (state: any) => any;
const getBarBaz4 = createSelector(
["foo.bar", "baz", { path: 0, argIndex: 2 }],
(bar, baz) => {
return `${bar} ${baz}`;
});
// getBarBaz4() has type signature: (...state: any[]) => any;
const getBarBazQux5 = createSelector<[State, string[]], string>(
["foo.bar", "baz", { path: 0, argIndex: 2 }],
(bar, baz) => {
return `${bar} ${baz}`;
});
// getBarBaz5() has type signature: (state_0: State, state_1: string[]) => string;
const getStucturedBarBaz = createSelector({
barBaz: getBarBaz,
});
// getStructuredBarBaz() has type signature: (state: any) => ({ barBaz: string });
Options
All the capabilities that exist withreselect
are still available using selectorator
, they are just passed as an object of options to createSelector
.deepEqual
defaults to falseA common usage of custom selectors is to perform a deep equality check instead of the standard strict equality check when comparing values. To apply this, simply set
deepEqual
to true
.import createSelector from "selectorator";
const selectoratorOptions = {
deepEqual: true
};
const getBaz = createSelector(
["foo.bar.baz"],
baz => {
return !!baz;
},
selectoratorOptions
);
isEqual
defaults to isSameValueZeroIf you want to use a custom equality comparator, pass the method as this option.
import createSelector from "selectorator";
const selectoratorOptions = {
// silly example checking current or next values related to "foo"
isEqual(currentFoo, nextFoo) {
return currentFoo === "foo" || nextFoo !== "foo";
}
};
const getFoo = createSelector(
["foo"],
foo => {
return !!foo;
},
selectoratorOptions
);
Please note that if this parameter is provided and
deepEqual
is also set to true
, deepEqual
will take priority and the isEqual
method will not be used.memoizer
defaults toreselect
defaultMemoizeIf you want to use a custom memoizer, pass the method as this option. This will use
createSelectorCreator
from reselect
internally, so consult their documentation on proper usage.import createSelector from "selectorator";
import moize from "moize";
const selectoratorOptions = {
memoizer: moize
};
const getFoo = createSelector(
["foo"],
foo => {
return !!foo;
},
selectoratorOptions
);
memoizerParams
defaults toreselect
allows you to pass parameters to the memoizer
function, and this array will translate directly into parameters 3
-n
. This is useful if your memoizer
uses something other than direct comparison for its equality test.import createSelector from "selectorator";
const selectoratorOptions = {
memoizer: memoizerThatChecksEqualToEachOtherOrToSpecificValuePassed,
memoizerParams: ["specificValue"]
};
const getFoo = createSelector(
["foo"],
foo => {
return !!foo;
},
selectoratorOptions
);
Development
Standard stuff, clone the repo andnpm install
dependencies. The npm scripts available:build
=> run webpack to build developmentdist
file with NODEENV=developmentbuild:minifed
=> run webpack to build productiondist
file with NODE
dev
=> run webpack dev server to run example app (playground!)docs
=> builds the docs via jsdoc
lint
=> run ESLint against all files in the src
folderprepublish
=> runs prepublish:compile
prepublish:compile
=> run lint
, test:coverage
, transpile
, build
, build:minified
, and docs
test
=> run AVA test functions with NODE_ENV=test
test:coverage
=> run test
but with nyc
for coverage checkertest:watch
=> run test
, but with persistent watchertranspile
=> run babel against all files in src
to create files in lib