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filter

The filter operator lets values through only when they pass a given test.

✅ Basic usage​

import { event } from "signux";
import { filter } from "signux/operators";

const numbers = event<number>();
const even = numbers.pipe(filter((n) => n % 2 === 0));

even.subscribe((n) => console.log("Even:", n));

numbers(1); // ignored
numbers(2); // logs: "Even: 2"

⚙️ How it works​

It subscribes to the source and applies the predicate function to every value.
If the predicate returns true, the value is emitted. Otherwise, it's ignored.

🧩 Use cases​

  • Filter out invalid or empty values
  • Skip duplicates or out-of-range numbers
  • Guard emissions based on state

📦 Signature​

function filter<T>(predicate: (value: T) => boolean): OperatorFn<T>;

🧪 Example with state​

const count = state(0);
const isEven = count.pipe(filter((n) => n % 2 === 0));
info

Note: filter() does not suppress the state value — it only affects reactive flows like pipe().subscribe(...).