use babel to transpile ts codes to es5 excluding plugins causing perf issue (#2415)

* fix TileLayer.forceReload

* use babel to transpile ts codes to es5 excluding plugins causing perf issue, fix #2397

Author: fuzhenn

babel.config.js

@@ -2,7 +2,12 @@ module.exports = {
   "presets": [
     ["@babel/env", {
       "loose": true,
-      "modules": false
+      "modules": false,
+      "exclude": [
+        "transform-destructuring",
+        "transform-spread",
+        "transform-parameters"
+      ]
     }]
   ],
   "plugins": [

rollup.config.js

@@ -35,6 +35,10 @@ const rollupPlugins = [
     commonjs(),
     typescript({
          sourceMap: true
+    }),
+    babel({
+        extensions: [".ts"],
+        babelHelpers: 'bundled'
     })
 ];
 

src/layer/tile/TileLayer.ts

@@ -257,7 +257,9 @@ class TileLayer extends Layer {
     forceReload() {
         this.fire('forcereloadstart');
         this.clear();
-        this.load();
+        if (this._renderer) {
+            this._renderer.setToRedraw();
+        }
         this.fire('forcereloadend');
         return this;
     }

tsconfig.json

@@ -19,7 +19,7 @@
     // ask tsc not to mess up with for ... of
     "downlevelIteration": true,
     "module": "esnext",
-    "target": "es5",
+    "target": "es6",
     "jsx": "preserve",
     "lib": [
       "es2015",