fix debug page and expose memory heap data

debug/debug.js

@@ -1,34 +1,44 @@
 
-var geojsonvt = require('../src/index.js');
+import geojsonvt from '../src/index.js';
+import {getHeapStatistics} from 'v8';
+import {readFileSync} from 'fs';
 
 console.time('load data');
-var data = require('./data/hrr.json');
+const data = JSON.parse(readFileSync(new URL('data/hrr.json', import.meta.url)));
 console.timeEnd('load data');
 
-var tileIndex = geojsonvt(data, {
+global.gc();
+const size = getHeapStatistics().used_heap_size;
+
+const tileIndex = geojsonvt(data, {
 	debug: 1
 });
 
+global.gc();
+console.log(`memory used: ${  Math.round((getHeapStatistics().used_heap_size - size) / 1024)  } KB`);
+
 console.time('drill down');
-for (var i = 0; i < 10; i++) {
-    for (var j = 0; j < 10; j++) {
+for (let i = 0; i < 10; i++) {
+    for (let j = 0; j < 10; j++) {
         tileIndex.getTile(7, 30 + i, 45 + j);
     }
 }
-for (var i = 0; i < 10; i++) {
-    for (var j = 0; j < 10; j++) {
+for (let i = 0; i < 10; i++) {
+    for (let j = 0; j < 10; j++) {
         tileIndex.getTile(8, 60 + i, 90 + j);
     }
 }
-for (var i = 0; i < 10; i++) {
-    for (var j = 0; j < 10; j++) {
+for (let i = 0; i < 10; i++) {
+    for (let j = 0; j < 10; j++) {
         tileIndex.getTile(10, 240 + i, 360 + j);
     }
 }
 console.timeEnd('drill down');
 
 console.log('tiles generated:', tileIndex.total, JSON.stringify(tileIndex.stats));
 
+global.gc();
+console.log(`memory used: ${  Math.round((getHeapStatistics().used_heap_size - size) / 1024)  } KB`);
 
 // tileIndex.maxZoom = 14;
 // tileIndex.getTile(14, 4100, 6200);