feat(view): Support to remove transform, close #53

Author: dengfuping

src/view.js

@@ -131,6 +131,12 @@ class View extends EventEmitter {
     me._executeTransform(options);
     return me;
   }
+  removeTransform(type) {
+    const me = this;
+    me.transforms = me.transforms.filter(item => item.type !== type);
+    me._reExecute();
+    return me;
+  }
   _executeTransform(options) {
     const me = this;
     options = me._preparseOptions(options);

test/unit/view-spec.js

@@ -122,4 +122,25 @@ describe('View', () => {
     });
     dv.source(populationChina);
   });
+
+  it('removeTransform', () => {
+    const dv = new View();
+    const data =
+`Expt,Run,Speed
+1,1,850
+1,2,740
+1,3,900
+1,4,1070`;
+    dv.source(data, {
+      type: 'csv'
+    }).transform({
+      type: 'filter',
+      callback(row) {
+        return row.Run !== '1';
+      }
+    });
+    expect(dv.transforms.length).to.equal(1);
+    dv.removeTransform('filter');
+    expect(dv.transforms.length).to.equal(0);
+  });
 });