Library rewrite

src/Feature.js

@@ -0,0 +1,34 @@
+const testRangeBounds = document => {
+    const TEST_HEIGHT = 123;
+
+    if (document.createRange) {
+        const range = document.createRange();
+        if (range.getBoundingClientRect) {
+            const testElement = document.createElement('boundtest');
+            testElement.style.height = `${TEST_HEIGHT}px`;
+            testElement.style.display = 'block';
+            document.body.appendChild(testElement);
+
+            range.selectNode(testElement);
+            const rangeBounds = range.getBoundingClientRect();
+            const rangeHeight = Math.round(rangeBounds.height);
+            document.body.removeChild(testElement);
+            if (rangeHeight === TEST_HEIGHT) {
+                return true;
+            }
+        }
+    }
+
+    return false;
+};
+
+const FEATURES = {
+    get SUPPORT_RANGE_BOUNDS() {
+        'use strict';
+        const value = testRangeBounds(document);
+        Object.defineProperty(FEATURES, 'SUPPORT_RANGE_BOUNDS', {value});
+        return value;
+    }
+};
+
+export default FEATURES;