setvalue to mdx (#1116)

src/content/docs/useform/setvalue.mdx

@@ -0,0 +1,177 @@
+---
+title: setValue
+description: Update field value
+sidebar: apiLinks
+---
+
+## \</> `setValue:` <TypeText>(name: string, value: unknown, config?: SetValueConfig) => void</TypeText>
+
+This function allows you to dynamically set the value of a <strong>registered</strong> field and have the options to validate and update the form state. At the same time, it tries to avoid unnecessary rerender.
+
+### Props
+
+---
+
+| Name                                     |                                                   | Description                                                                                                                                                                                                                                                                                                                                                                                              |
+| ---------------------------------------- | ------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `name`<br/><TypeText>string</TypeText>   |                                                   | Target a single field or field array by name.                                                                                                                                                                                                                                                                                                                                                            |
+| `value`<br/><TypeText>unknown</TypeText> |                                                   | The value for the field. This argument is required and can not be `undefined`.                                                                                                                                                                                                                                                                                                                           |
+| `options`                                | `shouldValidate`<br/><TypeText>boolean</TypeText> | <ul><li>Whether to compute if your input is valid or not (subscribed to <TypeText>errors</TypeText>).</li><li>Whether to compute if your entire form is valid or not (subscribed to <TypeText>isValid</TypeText>).</li>This option will update `touchedFields` at the specified field level not the entire form touched fields.</ul>                                                                     |
+|                                          | `shouldDirty`<br/><TypeText>boolean</TypeText>    | <ul><li>Whether to compute if your input is dirty or not against your `defaultValues` (subscribed to <TypeText>dirtyFields</TypeText>).</li><li>Whether to compute if your entire form is dirty or not against your `defaultValues` (subscribed to <TypeText>isDirty</TypeText>).</li><li>This option will update `dirtyFields` at the specified field level not the entire form dirty fields.</li></ul> |
+|                                          | `shouldTouch`<br/><TypeText>boolean</TypeText>    | Whether to set the input itself to be touched.                                                                                                                                                                                                                                                                                                                                                           |
+
+<Admonition type="important" title="Rules">
+
+- You can use methods such as [replace](/docs/usefieldarray#replace) or [update](/docs/usefieldarray#update) for field array, however, they will cause the component to unmount and remount for the targeted field array.
+
+  ```javascript
+  const { update } = useFieldArray({ name: "array" })
+
+  // unmount fields and remount with updated value
+  update(0, { test: "1", test1: "2" })
+
+  // will directly update input value
+  setValue("array.0.test1", "1")
+  setValue("array.0.test2", "2")
+  ```
+
+- The method will not create a new field when targeting a non-existing field.
+
+  ```javascript
+  const { replace } = useFieldArray({ name: "test" })
+
+  // ❌ doesn't create new input
+  setValue("test.101.data")
+
+  // ✅ work on refresh entire field array
+  replace([{ data: "test" }])
+  ```
+
+- Only the following conditions will trigger a re-render:
+
+  - When an error is triggered or corrected by a value update.
+  - When `setValue` cause state update, such as dirty and touched.
+
+- It's recommended to target the field's name rather than make the second argument a nested object.
+
+  ```javascript
+  setValue("yourDetails.firstName", "value") // ✅ performant
+  setValue("yourDetails", { firstName: "value" }) ❌ // less performant
+
+  register("nestedValue", { value: { test: "data" } }) // register a nested value input
+  setValue("nestedValue.test", "updatedData") // ❌ failed to find the relevant field
+  setValue("nestedValue", { test: "updatedData" }) // ✅ setValue find input and update
+  ```
+
+- It's recommended to register the input's name before invoking `setValue`. To update the entire `FieldArray`, make sure the `useFieldArray` hook is being executed first.
+
+  **Important:** use `replace` from `useFieldArray` instead, update entire field array with `setValue` will be removed in the next major version.
+
+  ```javascript
+  // you can update an entire Field Array,
+  setValue("fieldArray", [{ test: "1" }, { test: "2" }]) // ✅
+
+  // you can setValue to a unregistered input
+  setValue("notRegisteredInput", "value") // ✅ prefer to be registered
+
+  // the following will register a single input (without register invoked)
+  setValue("resultSingleNestedField", { test: "1", test2: "2" }) // 🤔
+
+  // with registered inputs, the setValue will update both inputs correctly.
+  register("notRegisteredInput.test", "1")
+  register("notRegisteredInput.test2", "2")
+  setValue("notRegisteredInput", { test: "1", test2: "2" }) // ✅ sugar syntax to setValue twice
+  ```
+
+</Admonition>
+
+### Examples
+
+---
+
+**Basic**
+
+```javascript sandbox="https://codesandbox.io/s/react-hook-form-v7-ts-setvalue-8z9hx"
+import { useForm } from "react-hook-form"
+
+const App = () => {
+  const { register, setValue } = useForm({
+    firstName: "",
+  })
+
+  return (
+    <form>
+      <input {...register("firstName", { required: true })} />
+      <button onClick={() => setValue("firstName", "Bill")}>setValue</button>
+      <button
+        onClick={() =>
+          setValue("firstName", "Luo", {
+            shouldValidate: true,
+            shouldDirty: true,
+          })
+        }
+      >
+        setValue options
+      </button>
+    </form>
+  )
+}
+```
+
+**Dependant Fields**
+
+```typescript sandbox="https://codesandbox.io/s/dependant-field-dwin1"
+import * as React from "react";
+import { useForm } from "react-hook-form";
+
+type FormValues = {
+  a: string;
+  b: string;
+  c: string;
+};
+
+export default function App() {
+  const { watch, register, handleSubmit, setValue, formState } = useForm<
+    FormValues
+  >({
+    defaultValues: {
+      a: "",
+      b: "",
+      c: ""
+    }
+  });
+  const onSubmit = (data: FormValues) => console.log(data);
+  const [a, b] = watch(["a", "b"]);
+
+  React.useEffect(() => {
+    if (formState.touchedFields.a && formState.touchedFields.b && a && b) {
+      setValue("c", `${a} ${b}`);
+    }
+  }, [setValue, a, b, formState]);
+
+  return (
+    <form onSubmit={handleSubmit(onSubmit)}>
+      <input {...register("a")} placeholder="a" />
+      <input {...register("b")} placeholder="b" />
+      <input {...register("c")} placeholder="c" />
+      <input type="submit" />
+
+      <button
+        type="button"
+        onClick={() => {
+          setValue("a", "what", { shouldTouch: true });
+          setValue("b", "ever", { shouldTouch: true });
+        }}
+      >
+        trigger value
+      </button>
+    </form>
+  );
+}
+```
+
+### Video
+
+---
+
+<YouTube youTubeId="qpv51sCH3fI" />