Enable strict mode

extensions/markdown/preview-src/index.ts

@@ -10,7 +10,7 @@ import { postCommand, postMessage } from './messaging';
 function throttle(fn: (x: any) => any, threshhold: any, scope?: any) {
 	threshhold = threshhold || (threshhold = 250);
 	var last: any, deferTimer: any;
-	return function (...x: any[]) {
+	return function (this: any, ...x: any[]) {
 		var context = scope || this;
 
 		var now = +new Date,
@@ -71,7 +71,7 @@ function getElementsForSourceLine(targetLine: number): { previous: CodeLineEleme
 	let previous = lines[0] || null;
 	for (const entry of lines) {
 		if (entry.line === lineNumber) {
-			return { previous: entry, next: null };
+			return { previous: entry, next: undefined };
 		}
 		else if (entry.line > lineNumber) {
 			return { previous, next: entry };
@@ -163,14 +163,14 @@ class ActiveLineMarker {
 		this._current = before;
 	}
 
-	_unmarkActiveElement(element: HTMLElement) {
+	_unmarkActiveElement(element: HTMLElement | undefined) {
 		if (!element) {
 			return;
 		}
 		element.className = element.className.replace(/\bcode-active-line\b/g, '');
 	}
 
-	_markActiveElement(element: HTMLElement) {
+	_markActiveElement(element: HTMLElement | undefined) {
 		if (!element) {
 			return;
 		}
@@ -250,7 +250,7 @@ document.addEventListener('dblclick', event => {
 
 	const offset = event.pageY;
 	const line = getEditorLineNumberForPageOffset(offset);
-	if (!isNaN(line)) {
+	if (typeof line === 'number' && !isNaN(line)) {
 		postMessage('didClick', { line });
 	}
 });
@@ -260,8 +260,6 @@ document.addEventListener('click', event => {
 		return;
 	}
 
-	const baseElement = document.getElementsByTagName('base')[0];
-
 	let node: any = event.target;
 	while (node) {
 		if (node.tagName && node.tagName === 'A' && node.href) {
@@ -287,7 +285,7 @@ if (settings.scrollEditorWithPreview) {
 			scrollDisabled = false;
 		} else {
 			const line = getEditorLineNumberForPageOffset(window.scrollY);
-			if (!isNaN(line)) {
+			if (typeof line === 'number' && !isNaN(line)) {
 				postMessage('revealLine', { line });
 			}
 		}

extensions/markdown/preview-src/loading.ts

@@ -2,13 +2,10 @@
  *  Copyright (c) Microsoft Corporation. All rights reserved.
  *  Licensed under the MIT License. See License.txt in the project root for license information.
  *--------------------------------------------------------------------------------------------*/
-import { getSettings } from './settings';
 import { postCommand } from './messaging';
 
 const unloadedStyles: string[] = [];
 
-const settings = getSettings();
-
 const onStyleLoadError = (event: any) => {
 	const source = event.target.dataset.source;
 	unloadedStyles.push(source);

extensions/markdown/preview-src/settings.ts

@@ -7,12 +7,19 @@ export interface PreviewSettings {
 	source: string;
 	line: number;
 	lineCount: number;
-	scrollPreviewWithEditor: boolean;
+	scrollPreviewWithEditor?: boolean;
 	scrollEditorWithPreview: boolean;
 	disableSecurityWarnings: boolean;
 	doubleClickToSwitchToEditor: boolean;
 }
 
 export function getSettings(): PreviewSettings {
-	return JSON.parse(document.getElementById('vscode-markdown-preview-data').getAttribute('data-settings'));
+	const element = document.getElementById('vscode-markdown-preview-data');
+	if (element) {
+		const data = element.getAttribute('data-settings');
+		if (data) {
+			return JSON.parse(data);
+		}
+	}
+	throw new Error('Could not load settings');
 }

extensions/markdown/preview-src/strings.ts

@@ -4,5 +4,12 @@
  *--------------------------------------------------------------------------------------------*/
 
 export function getStrings(): { [key: string]: string } {
-	return JSON.parse(document.getElementById('vscode-markdown-preview-data').getAttribute('data-strings'));
+	const store = document.getElementById('vscode-markdown-preview-data');
+	if (store) {
+		const data = store.getAttribute('data-strings');
+		if (data) {
+			return JSON.parse(data);
+		}
+	}
+	throw new Error('Could not load strings');
 }

extensions/markdown/preview-src/tsconfig.json

 {
 	"compilerOptions": {
 		"outDir": "./dist/",
-		"noImplicitAny": true,
 		"module": "es6",
 		"target": "es6",
 		"jsx": "react",
-		"sourceMap": true
+		"sourceMap": true,
+		"strict": true,
+		"noImplicitAny": true,
+		"noUnusedLocals": true
 	}
 }
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