Can not override safari's default search in safari app extension?

Question

I am developing safari app extension in Xcode using swift language to take over default search to my site.

I have updated info.plist file to inject script.js file in every page as using SFSafariContentScript.

I have tried using below code in script.js file to add event to default search box, but its not working(It was working in legacy Safari extension).

safari.application.addEventListener("beforeSearch", getSearchText, true);
function getSearchText(e) {
    alert("hi, this is from search box");
}

Does safari app extension have support to adding events to search bar ? Any help on this is appreciated.

Thanks in Advance!