Add clearOutputs() method to ISharedCodeCell (#330)

* add-clearOutputs-method

* add-test

Author: Darshan808

javascript/src/api.ts

@@ -572,6 +572,11 @@ export interface ISharedCodeCell
     outputs: Array<nbformat.IOutput>
   ): void;
 
+  /**
+   * Clear all outputs from the cell.
+   */
+  clearOutputs(origin: any): void;
+
   /**
    * Serialize the model to JSON.
    */

javascript/src/ycell.ts

@@ -867,6 +867,19 @@ export class YCodeCell
     );
   }
 
+  /**
+   * Clear all outputs from the cell.
+   */
+  clearOutputs(origin: any = null): void {
+    this.transact(
+      () => {
+        this._youtputs.delete(0, this._youtputs.length);
+      },
+      false,
+      origin
+    );
+  }
+
   /**
    * Serialize the model to JSON.
    */

javascript/test/ycell.spec.ts

@@ -333,3 +333,22 @@ describe('@jupyter/ydoc', () => {
     });
   });
 });
+
+test('should clear outputs from a code cell', () => {
+  const codeCell = YCodeCell.create();
+  const outputs = [
+    {
+      data: {
+        'text/plain': ['Hello, world!']
+      },
+      metadata: {},
+      output_type: 'execute_result'
+    }
+  ];
+
+  codeCell.setOutputs(outputs);
+  expect(codeCell.getOutputs()).toEqual(outputs);
+
+  codeCell.clearOutputs();
+  expect(codeCell.getOutputs()).toEqual([]);
+});