fix(tooltip): fix code format and check if dom is supported before `testStyle`.

src/component/tooltip/helper.ts

@@ -20,6 +20,7 @@
 import { TooltipOption } from './TooltipModel';
 import Model from '../../model/Model';
 import { toCamelCase } from '../../util/format';
+import env from 'zrender/src/core/env';
 
 /* global document */
 
@@ -32,35 +33,38 @@ export function shouldTooltipConfine(tooltipModel: Model<TooltipOption>): boolea
 }
 
 function testStyle(styleProps: string[]): string | undefined {
-	const style = document.documentElement.style;
-	for (let i = 0, len = styleProps.length; i < len; i++) {
-		if (styleProps[i] in style) {
-			return styleProps[i];
-		}
-	}
+    if (!env.domSupported) {
+        return;
+    }
+    const style = document.documentElement.style;
+    for (let i = 0, len = styleProps.length; i < len; i++) {
+        if (styleProps[i] in style) {
+            return styleProps[i];
+        }
+    }
 }
 
 export const TRANSFORM_VENDOR = testStyle(
-	['transform', 'webkitTransform', 'OTransform', 'MozTransform', 'msTransform']
+    ['transform', 'webkitTransform', 'OTransform', 'MozTransform', 'msTransform']
 );
 
 export const TRANSITION_VENDOR = testStyle(
-	['webkitTransition', 'transition', 'OTransition', 'MozTransition', 'msTransition']
+    ['webkitTransition', 'transition', 'OTransition', 'MozTransition', 'msTransition']
 );
 
 export function toCSSVendorPrefix(styleVendor: string, styleProp: string) {
-	styleProp = toCamelCase(styleProp, true);
-	const idx = styleVendor.indexOf(styleProp);
-	styleVendor = idx === -1
-		? styleProp
-		: `-${styleVendor.slice(0, idx)}-${styleProp}`;
-	return styleVendor.toLowerCase();
+    styleProp = toCamelCase(styleProp, true);
+    const idx = styleVendor.indexOf(styleProp);
+    styleVendor = idx === -1
+        ? styleProp
+        : `-${styleVendor.slice(0, idx)}-${styleProp}`;
+    return styleVendor.toLowerCase();
 }
 
 export function getComputedStyle(el: HTMLElement, style?: string) {
-	const stl = (el as any).currentStyle
-		|| (document.defaultView && document.defaultView.getComputedStyle(el));
-	return stl
-		? style ? stl[style] : stl
-		: null;
+    const stl = (el as any).currentStyle
+        || (document.defaultView && document.defaultView.getComputedStyle(el));
+    return stl
+        ? style ? stl[style] : stl
+        : null;
 }