init

1 files changed, 34 insertions, 0 deletions

diff --git a/src/observable.ts b/src/observable.ts
new file mode 100644
index 0000000..3e1308c
--- /dev/null
+++ b/src/observable.ts
@@ -0,0 +1,34 @@
+/*
+    This file is part of jshelper (https://codeberg.org/metamuffin/jshelper)
+    which is licensed under the GNU Affero General Public License (version 3); see /COPYING.
+    Copyright (C) 2023 metamuffin <metamuffin.org>
+*/
+export class OVar<T> {
+    private _value: T
+    private observers: ((v: T) => unknown)[] = []
+
+    constructor(initial: T) {
+        this._value = initial;
+    }
+
+    get value() { return this._value }
+    set value(v: T) {
+        this._value = v;
+        this.observers.forEach(o => o(v))
+    }
+
+    onchange(handler: (v: T) => unknown): () => unknown {
+        this.observers.push(handler)
+        return () => this.observers = this.observers.filter(o => o != handler)
+    }
+    onchangeinit(handler: (v: T) => unknown): () => unknown {
+        const abort = this.onchange(handler)
+        handler(this.value)
+        return abort
+    }
+    map<U>(fn: (v: T) => U): OVar<U> {
+        const uv = new OVar(fn(this.value))
+        this.onchange(v => uv.value = fn(v))
+        return uv;
+    }
+}