1 files changed, 61 insertions, 0 deletions
diff --git a/index.js b/index.js
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index 0000000..e98a636
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+++ b/index.js
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+// Credit Ryan Carniato https://frontendmasters.com/courses/reactivity-solidjs/
+
+let context = [];
+
+export function untrack(fn) {
+    const prevContext = context;
+    context = [];
+    const res = fn();
+    context = prevContext;
+    return res;
+}
+
+function cleanup(observer) {
+    for (const dep of observer.dependencies) {
+        dep.delete(observer);
+    }
+    observer.dependencies.clear();
+}
+
+function subscribe(observer, subscriptions) {
+    subscriptions.add(observer);
+    observer.dependencies.add(subscriptions);
+}
+
+export function createSignal(value) {
+    const subscriptions = new Set();
+
+    const read = () => {
+        const observer = context[context.length - 1]
+        if (observer) subscribe(observer, subscriptions);
+        return value;
+    }
+    const write = (newValue) => {
+        value = newValue;
+        for (const observer of [...subscriptions]) {
+            observer.execute();
+        }
+    }
+
+    return [read, write];
+}
+
+export function createEffect(fn) {
+    const effect = {
+        execute() {
+            cleanup(effect);
+            context.push(effect);
+            fn();
+            context.pop();
+        },
+        dependencies: new Set()
+    }
+
+    effect.execute();
+}
+
+export function createMemo(fn) {
+    const [signal, setSignal] = createSignal();
+    createEffect(() => setSignal(fn()));
+    return signal;
+}