InAppBroswer: Uncaught SyntaxError: Block-scoped declarations .. not yet supported when loading js on Android App. outside strict mode

Question

I am getting error

Uncaught SyntaxError: Block-scoped declarations (let, const, function, class) not yet supported outside strict mode

when the following js is added to the html head,

;
;frappe.socket = {
   open_tasks: {},
   open_docs: [],
   emit_queue: [],
   ...
   doc_open: function(doctype, docname) {
       "use strict";
       if (!frappe.socket.last_doc || (frappe.socket.last_doc[0] != doctype && frappe.socket.last_doc[0] != docname)) {
           frappe.socket.socket.emit('doc_open', doctype, docname);
       }
       frappe.socket.last_doc = [doctype, docname];
   },
   ...
}

Note I added "use strict"; based on existing stackoverflow threads. I am still getting the error. The chrome debugger points at the below line.

     frappe.socket.last_doc = [doctype, docname];

The browser is a cordova app, running in Android Studio Emulator. I think it is using InAppBrowser. The remaining js fails to load after this error. I am not sure which code needs strict mode.

The same code runs fine without "use strict" in chrome, Edge, FF.

Answer 1

Found the issue: Even though the Google Chrome Developer Window was showing this line, This line was the first statement in the minified JS line.

On looking at the complete Minified JS line, I found the issue is in another line later,

frappe.socket.file_watcher.on('reload_css', function(filename) { 
    let abs_file_path = "assets/" + filename; 

Adding "use strict at the start of this function fixed the issue. –