Merge pull request #448 from contentstack/VE-6722-init-optimisation

Optimisation: `init` to emit postMessage on `DOMContentLoaded`

Author: csAyushDubey

src/livePreview/__test__/live-preview.test.ts

@@ -460,7 +460,7 @@ describe("testing window event listeners", () => {
         document.body.appendChild(descPara);
         document.body.appendChild(linkPara);
 
-        addEventListenerMock = vi.spyOn(window, "addEventListener");
+        addEventListenerMock = vi.spyOn(document, "addEventListener");
     });
 
     afterEach(() => {
@@ -482,7 +482,7 @@ describe("testing window event listeners", () => {
         livePreviewInstance = new LivePreview();
 
         expect(addEventListenerMock).toBeCalledWith(
-            "load",
+            "DOMContentLoaded",
             expect.any(Function)
         );
         readyState.mockRestore();

src/livePreview/live-preview.ts

@@ -39,10 +39,13 @@ export default class LivePreview {
 
         if (config.enable) {
             if (
-                typeof document !== undefined &&
-                document.readyState === "complete"
+                typeof document !== undefined
             ) {
-                this.requestDataSync();
+                if(document.readyState === "interactive" || document.readyState === "complete"){
+                    this.requestDataSync();
+                } else {
+                    document.addEventListener("DOMContentLoaded", this.requestDataSync);
+                }
             } else {
                 window.addEventListener("load", this.requestDataSync);
             }