@clipboard-health/rules-engine
v1.16.2
Published
A pure functional rules engine to keep logic-dense code simple, reliable, understandable, and explainable.
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@clipboard-health/rules-engine
A pure functional rules engine to keep logic-dense code simple, reliable, understandable, and explainable.
The engine uses static rules created in code instead of dynamic rules serialized to a database since we haven't needed the latter yet.
Table of contents
Install
npm install @clipboard-health/rules-engine
Usage
import { deepEqual } from "node:assert/strict";
import {
all,
appendOutput,
firstMatch,
type Rule,
type RuleContext,
} from "@clipboard-health/rules-engine";
interface Input {
a: number;
b: number;
}
interface Output {
result: number;
}
const exampleContext: RuleContext<Input, Output> = {
input: {
a: 2,
b: 5,
},
output: [],
};
const addNumbersIfPositiveRule: Rule<Input, Output> = {
runIf: (input) => input.a > 0 && input.b > 0,
run: (context) => {
const { a, b } = context.input;
return appendOutput(context, { result: a + b });
},
};
const multiplyNumbersIfPositiveRule: Rule<Input, Output> = {
runIf: (input) => input.a > 0 && input.b > 0,
run: (context) => {
const { a, b } = context.input;
return appendOutput(context, { result: a * b });
},
};
const divideNumbersIfNegative: Rule<Input, Output> = {
runIf: (input) => input.a < 0 && input.b < 0,
run: (context) => {
const { a, b } = context.input;
return appendOutput(context, { result: a / b });
},
};
// Using all() applies all the rules to the context
const allResult = all(
addNumbersIfPositiveRule,
divideNumbersIfNegative,
multiplyNumbersIfPositiveRule,
).run(exampleContext);
deepEqual(allResult.output, [{ result: 7 }, { result: 10 }]);
// Using firstMatch() applies the first the rules to the context
const firstMatchResult = firstMatch(
divideNumbersIfNegative,
addNumbersIfPositiveRule,
multiplyNumbersIfPositiveRule,
).run(exampleContext);
deepEqual(firstMatchResult.output, [{ result: 7 }]);
Local development commands
See package.json
scripts
for a list of commands.