Update FieldArray.md

Author: Kuldeep Saxena

docs/api/FieldArray.md

@@ -1 +1,78 @@
 
+
+# FieldArray
+A react component which creates a new or can be used with an existing [FormArray](FormArray.md) control.
+
+## How it works
+ - It creates a new instance of [FormArray](FormArray.md) in absence of the `name` and `control` props.
+ - If a `name` prop is defined then it means that the control has to be added in an already existing parent control (  [FormGroup](FormGroup.md) / [FormArray](FormArray.md)) i.e the parent control must be present.
+ - If a control with the same name is already present in the parent control then it just returns the same otherwise it'll create a new instance of [FormArray](FormArray.md) class. 
+ - You can define a parent control either by passing the `parent` prop or using the component as a child of the `FieldArray` or `FieldGroup` component.
+ - If a `control` prop is defined then it just returns the same.
+
+
+## Props
+```ts
+strict: boolean;
+```
+Default value: `true`
+
+If `true` then it'll only re-render the component only when any change happens in the form array control irrespective of the parent component(state and props) changes.
+
+##
+
+```ts
+    render: (control: FormArray|FormControl|FormGroup) => React.ReactElement<any>|React.ReactElement<any>[];
+```
+A render function prop which returns a react component which needs to be re-render whenever the control state changes.
+You can also pass a render function as a child.
+For eg.
+
+```ts
+  <FieldArray ...>
+  {
+    (control) => <SomeComponent/>
+  }
+  </FieldArray>
+```
+
+##
+```ts
+control: AbstractControl;
+```
+An instance of [FormArray](FormArray.md) control.
+
+##
+```ts
+name: string;
+```
+Name of the control.
+
+##
+```ts
+index: number
+```
+To define at which index the controls has to be inserted if the parent control is an instance of [FormArray](FormArray.md).
+
+##
+```ts
+options: AbstractControlOptions;
+```
+You can pass the [AbstractControlOptions](AbstractControlOptions.md) as `options` props.
+
+For eg.
+
+```ts
+<FieldArray
+  options={{
+    validators: Validators.required,
+    updateOn: 'blur'
+  }}
+/>
+```
+
+##
+```ts
+parent: AbstractControl;
+```
+An instance of FormGroup or FormArray class as a parent control.