Merge pull request #18 from datavis-tech/set-only-changed

Only Propagate Changed Properties
datavis-tech · Aug 28, 2018 · eb56e77 · eb56e77
2 parents 1f6a264 + 4103323
commit eb56e77
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Showing 2 changed files with 23 additions and 2 deletions.
diff --git a/src/index.js b/src/index.js
@@ -16,8 +16,10 @@ const Topologica = options => {
   };
 
   const setProperty = ([property, value]) => {
-    values.set(property, value);
-    changed.add(property);
+    if (values.get(property) !== value) {
+      values.set(property, value);
+      changed.add(property);
+    }
   };
 
   const set = options => {

diff --git a/test/test.js b/test/test.js
@@ -240,4 +240,23 @@ describe('Topologica.js', () => {
       a: 5
     });
   });
+
+  it('Should only propagate changes when values change.', () => {
+    let invocations = 0;
+
+    const state = Topologica({
+      b: λ(({a}) => invocations++, 'a')
+    });
+
+    assert.equal(invocations, 0);
+
+    state.set({ a: 2 });
+    assert.equal(invocations, 1);
+
+    state.set({ a: 2 });
+    assert.equal(invocations, 1);
+
+    state.set({ a: 99 });
+    assert.equal(invocations, 2);
+  });
 });