liftA2

1 files changed, 7 insertions, 0 deletions

diff --git a/src/observable.ts b/src/observable.ts
index a9e23e8..bd66963 100644
--- a/src/observable.ts
+++ b/src/observable.ts
@@ -41,6 +41,13 @@ export class OVar<T> {
         uv.weak = true
         return uv;
     }
+    liftA2<U, V>(other: OVar<U>, fn: (x: T, y: U) => V): OVar<V> {
+        const uv = new OVar(fn(this.value, other.value))
+        uv.cancel_source = this.onchange(x => uv.value = fn(x, other.value))
+        uv.cancel_source = other.onchange(y => uv.value = fn(this.value, y))
+        uv.weak = true
+        return uv;
+    }
     wait_for(val: T) {
         return new Promise<void>(r => {
             const abort = this.onchangeinit(v => {