Add Update Formik Initial Values When Props Change as a react til

react/update-formik-initial-values-when-props-change.md

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+# Update Formik Initial Values When Props Change
+
+When a [Formik](https://jaredpalmer.com/formik/) form mounts, whatever the
+initial values are set to is what they will be. Even if the initial values are
+computed from props, those props changing will not affect `initialValues` after
+mount.
+
+```javascript
+const ZipForm = ({ currentZip }) => {
+  return (
+    <Formik
+      initialValues={{ zip: currentZip }}
+      onSubmit={(values, actions) => {
+        // do stuff
+      }}
+      ...
+```
+
+If we are fetching the user's saved zip code asynchronously from a server while
+the form is first being rendered, then `currentZip` will start as an empty
+value. Once the async request comes back and `currentZip` is set, we won't see
+the form update the `zip` field.
+
+There was a time when you would have to jump through some hoops to make sure
+the freshest prop value made it into the form. Now, Formik provides a handier
+mechanism -- the `enableReinitialize` prop.
+
+```javascript
+const ZipForm = ({ currentZip }) => {
+  return (
+    <Formik
+      initialValues={{ zip: currentZip }
+      enableReinitialize
+      onSubmit={(values, actions) => {
+        // do stuff
+      }}
+      ...
+```
+
+By setting `enableReinitialize` to true, we are telling Formik that any prop
+changes that flow into the `initialValues` object should cause those values to
+be _reinitialized_.
+
+See a [live example](https://codesandbox.io/s/sad-mendeleev-4dbbp).