Add data statistics script for MDN 2019 key result goal

package.json

@@ -39,6 +39,7 @@
   "scripts": {
     "confluence": "node ./node_modules/mdn-confluence/main/generate.es6.js --output-dir=. --bcd-module=./index.js",
     "lint": "node test/lint",
+    "stats": "node scripts/statistics",
     "release-notes": "node scripts/release-notes",
     "render": "node scripts/render",
     "show-errors": "npm test 1> /dev/null",

scripts/statistics.js

@@ -0,0 +1,80 @@
+'use strict';
+const bcd = require('..');
+
+const browsers = ['chrome', 'chrome_android', 'edge', 'firefox', 'ie', 'safari', 'safari_ios', 'webview_android'];
+let stats = { total: { all: 0, true: 0, null: 0, real: 0 } };
+browsers.forEach(browser => {
+  stats[browser] = { all: 0, true: 0, null: 0, real: 0 }
+});
+
+const checkSupport = (supportData, type) => {
+  if (!Array.isArray(supportData)) {
+    supportData = [supportData];
+  }
+  return supportData.some(item => item.version_added === type || item.version_removed === type)
+};
+
+const processData = (data) => {
+  if (data.support) {
+    browsers.forEach(function(browser) {
+      stats[browser].all++;
+      stats.total.all++;
+      let real_value = true;
+      if (!data.support[browser]) {
+        stats[browser].null++;
+        stats.total.null++;
+        real_value = false;
+      } else {
+        if (checkSupport(data.support[browser], null)) {
+          stats[browser].null++;
+          stats.total.null++;
+          real_value = false;
+        }
+        if (checkSupport(data.support[browser], true)) {
+          stats[browser].true++;
+          stats.total.true++;
+          real_value = false;
+        }
+      }
+      if (real_value) {
+        stats[browser].real++;
+        stats.total.real++;
+      }
+    });
+  }
+};
+
+const iterateData = (data) => {
+  for (let key in data) {
+    if (key === '__compat') {
+      processData(data[key]);
+    } else {
+      iterateData(data[key]);
+    }
+  }
+};
+
+for (let data in bcd) {
+  if (!(data === 'browsers' || data === 'webextensions')) {
+    iterateData(bcd[data]);
+  }
+}
+
+const printTable = () => {
+  let table = `| browser | real values | \`true\` values | \`null\` values |
+| --- | --- | --- | --- |
+`;
+
+  Object.keys(stats).forEach(entry => {
+    table += `| ${entry.replace('_', ' ')} | `;
+    table += `${((stats[entry].real / stats[entry].all) * 100).toFixed(2)}% | `;
+    table += `${((stats[entry].true / stats[entry].all) * 100).toFixed(2)}% | `;
+    table += `${((stats[entry].null / stats[entry].all) * 100).toFixed(2)}% |
+`;
+  });
+
+  console.log(table);
+}
+
+console.log('Status as of version 0.0.xx (released on xx/xx/2019) for web platform features: \n')
+printTable();