feature(slate): Add isElementType utility function to Element Interfa…

…ce (#4349)

.changeset/rich-wasps-leave.md

@@ -0,0 +1,5 @@
+---
+'slate': patch
+---
+
+Add isElementType utility to Element interface

packages/slate/src/interfaces/element.ts

@@ -18,9 +18,25 @@ export interface ElementInterface {
   isElement: (value: any) => value is Element
   isElementList: (value: any) => value is Element[]
   isElementProps: (props: any) => props is Partial<Element>
+  isElementType: <T extends Element>(
+    value: any,
+    elementVal: string,
+    elementKey?: string
+  ) => value is T
   matches: (element: Element, props: Partial<Element>) => boolean
 }
 
+/**
+ * Shared the function with isElementType utility
+ */
+const isElement = (value: any): value is Element => {
+  return (
+    isPlainObject(value) &&
+    Node.isNodeList(value.children) &&
+    !Editor.isEditor(value)
+  )
+}
+
 export const Element: ElementInterface = {
   /**
    * Check if a value implements the 'Ancestor' interface.
@@ -34,14 +50,7 @@ export const Element: ElementInterface = {
    * Check if a value implements the `Element` interface.
    */
 
-  isElement(value: any): value is Element {
-    return (
-      isPlainObject(value) &&
-      Node.isNodeList(value.children) &&
-      !Editor.isEditor(value)
-    )
-  },
-
+  isElement,
   /**
    * Check if a value is an array of `Element` objects.
    */
@@ -58,6 +67,19 @@ export const Element: ElementInterface = {
     return (props as Partial<Element>).children !== undefined
   },
 
+  /**
+   * Check if a value implements the `Element` interface and has elementKey with selected value.
+   * Default it check to `type` key value
+   */
+
+  isElementType: <T extends Element>(
+    value: any,
+    elementVal: string,
+    elementKey: string = 'type'
+  ): value is T => {
+    return isElement(value) && value[elementKey] === elementVal
+  },
+
   /**
    * Check if an element matches set of properties.
    *

packages/slate/test/interfaces/Element/isElement/isElementDiscriminant.tsx

@@ -0,0 +1,10 @@
+import { Element } from 'slate'
+
+export const input = {
+  source: 'heading-large',
+  children: [{ text: '' }],
+}
+export const test = value =>
+  Element.isElementType(value, 'heading-large', 'source')
+
+export const output = true

packages/slate/test/interfaces/Element/isElement/isElementDiscriminantFalse.tsx

@@ -0,0 +1,9 @@
+import { Element } from 'slate'
+
+export const input = {
+  type: 'heading-large',
+  children: [{ text: '' }],
+}
+export const test = value => Element.isElementType(value, 'paragraph', 'source')
+
+export const output = false

packages/slate/test/interfaces/Element/isElement/isElementType.tsx

@@ -0,0 +1,9 @@
+import { Element } from 'slate'
+
+export const input = {
+  type: 'paragraph',
+  children: [{ text: '' }],
+}
+export const test = value => Element.isElementType(value, 'paragraph')
+
+export const output = true

packages/slate/test/interfaces/Element/isElement/isElementTypeFalse.tsx

@@ -0,0 +1,9 @@
+import { Element } from 'slate'
+
+export const input = {
+  type: 'heading-large',
+  children: [{ text: '' }],
+}
+export const test = value => Element.isElementType(value, 'paragraph')
+
+export const output = false