Add hasPrevious method to Path (#3963)

* Add hasPrevious method to Path API.

Co-authored-by: Mitchell Donaldson <mitch@nod.money>

packages/slate/src/interfaces/path.ts

@@ -118,6 +118,14 @@ export const Path = {
     )
   },
 
+  /**
+   * Check if the path of previous sibling node exists
+   */
+
+  hasPrevious(path: Path): boolean {
+    return path[path.length - 1] > 0
+  },
+
   /**
    * Check if a path is after another.
    */

packages/slate/test/interfaces/Path/hasPrevious/root.tsx

@@ -0,0 +1,7 @@
+import { Path } from 'slate'
+
+export const input = [0, 0]
+export const test = path => {
+  return Path.hasPrevious(path)
+}
+export const output = false

packages/slate/test/interfaces/Path/hasPrevious/success.tsx

@@ -0,0 +1,7 @@
+import { Path } from 'slate'
+
+export const input = [0, 1]
+export const test = path => {
+  return Path.hasPrevious(path)
+}
+export const output = true