Add useStateDelayed hook (#106)

Add useDelayedState hook

Co-authored-by: Angelos Chalaris <chalarangelo@gmail.com>

snippets/useDelayedState.md

@@ -0,0 +1,65 @@
+---
+title: useDelayedState
+tags: hooks,state,effect,intermediate
+firstSeen: 2021-12-15T05:00:00-04:00
+---
+
+Delays creating a stateful value until some condition is met.
+
+- Use the `useState()` hook to create a stateful value containing the actual `state` and a boolean, `loaded`.
+- Use the `useEffect()` hook to update the stateful value if the `condition` or `loaded` changes.
+- Create a function, `updateState`, that only updates the `state` value if `loaded` is truthy.
+
+```jsx
+const useDelayedState = (initialState, condition) => {
+  const [{ state, loaded }, setState] = React.useState({
+    state: null,
+    loaded: false,
+  });
+
+  React.useEffect(() => {
+    if (!loaded && condition) setState({ state: initialState, loaded: true });
+  }, [condition, loaded]);
+
+  const updateState = newState => {
+    if (!loaded) return;
+    setState({ state: newState, loaded });
+  };
+
+  return [state, updateState];
+};
+```
+
+```jsx
+const App = () => {
+  const [branches, setBranches] = React.useState([]);
+  const [selectedBranch, setSelectedBranch] = useDelayedState(
+    branches[0],
+    branches.length
+  );
+
+  React.useEffect(() => {
+    const handle = setTimeout(() => {
+      setBranches(['master', 'staging', 'test', 'dev']);
+    }, 2000);
+    return () => {
+      handle && clearTimeout(handle);
+    };
+  }, []);
+
+  return (
+    <div>
+      <p>Selected branch: {selectedBranch}</p>
+      <select onChange={e => setSelectedBranch(e.target.value)}>
+        {branches.map(branch => (
+          <option key={branch} value={branch}>
+            {branch}
+          </option>
+        ))}
+      </select>
+    </div>
+  );
+};
+
+ReactDOM.render(<App />, document.getElementById('root'));
+```