Issue 4795 - Use modern JavaScript syntax

qunit/tests/filterValidation.js

 "use strict";
 
 {
-  let filterValidation = require("filterValidation");
-  let parseFilter = filterValidation.parseFilter;
-  let parseFilters = filterValidation.parseFilters;
-
-  let filterClasses = require("filterClasses");
-  let BlockingFilter = filterClasses.BlockingFilter;
-  let ElemHideFilter = filterClasses.ElemHideFilter;
-  let CommentFilter = filterClasses.CommentFilter;
+  const {parseFilter, parseFilters} = require("filterValidation");
+  const {BlockingFilter,
+         ElemHideFilter,
+         CommentFilter} = require("filterClasses");
 
   module("Filter validation");
 
   test("Detecting invalid filters", () =>
   {
     equal(parseFilter("||example.com^$unknown").error.type, "invalid-filter", "unknown option");
     equal(parseFilter("[foobar]").error.type, "unexpected-filter-list-header", "filter list header");
     equal(parseFilter("##[foo").error.type, "invalid-css-selector", "invalid selector");
     ok(/\b4\b/.test(parseFilters("!comment\r\n||example.com^\n\n##/").errors[0]), "error contains corresponding line number");
   });
@@ skipping 38 matching lines @@
     ok(result.filters[0] instanceof BlockingFilter, "1st filter is blocking");
     equal(result.filters[0].text, "||example.com^", "1st filter text matches");
 
     ok(result.filters[1] instanceof ElemHideFilter, "2nd filter is elemhide");
     equal(result.filters[1].text, "###foobar",      "2nd filter text matches");
 
     ok(result.filters[2] instanceof CommentFilter,  "3rd filter is comment");
     equal(result.filters[2].text, "! foo bar",      "3rd filter text matches");
   });
 }