add URLSearchParams polyfill

package-lock.json

@@ -5011,6 +5011,11 @@
         }
       }
     },
+    "url-search-params": {
+      "version": "0.10.0",
+      "resolved": "https://registry.npmjs.org/url-search-params/-/url-search-params-0.10.0.tgz",
+      "integrity": "sha512-oFPzmbPAbdthStgffGq8alULe47skPDt1X3KW6NOQnKkcLHP4IS1NfdfHG/CBP5lGsr2gDzNp87pfWLx/eIxjw=="
+    },
     "util": {
       "version": "0.10.3",
       "resolved": "https://registry.npmjs.org/util/-/util-0.10.3.tgz",

package.json

@@ -27,6 +27,7 @@
     "svelte": "^1.50.0",
     "svelte-loader": "^2.3.3",
     "uglifyjs-webpack-plugin": "^1.1.5",
+    "url-search-params": "^0.10.0",
     "webpack": "^3.10.0"
   },
   "engines": {

templates/main.js

@@ -1,4 +1,17 @@
 import { init } from 'sapper/runtime.js';
 
+// polyfills
+Promise.all([
+  typeof URLSearchParams === 'undefined' && import('url-search-params').then(Params => {
+    window.URLSearchParams = Params
+    Object.defineProperty(window.URL.prototype, 'searchParams', {
+      get() {
+        return new Params(this.search)
+      }
+    })
+  })
+]).then(() => {
+  console.log('done')
   // `routes` is an array of route objects injected by Sapper
-init(document.querySelector('#sapper'), __routes__);
+  init(document.querySelector('#sapper'), __routes__)
+})