@@ -672,24 +672,23 @@
 "lint": "tslint --project tsconfig.json -e src/*.d.ts -t verbose"
 },
 "devDependencies": {
-"@types/fs-extra": "5.0.0",
-"@types/highlight.js": "^9.12.3",
-"@types/lodash": "^4.14.123",
+"@types/fs-extra": "^9.0.11",
+"@types/lodash": "^4.14.170",
 "@types/markdown-it": "0.0.7",
 "@types/mocha": "^2.2.42",
-"@types/node": "^7.0.43",
+"@types/node": "^14.14.33",
 "@types/require-from-string": "^1.2.0",
 "@types/vscode": "1.42.0",
-"tslint": "^5.9.1",
-"typescript": "^2.6.1"
+"tslint": "^5.20.1",
+"typescript": "^4.3.2"
 },
 "dependencies": {
-"fs-extra": "^6.0.1",
-"highlight.js": "^9.15.6",
-"lodash": "^4.17.19",
+"fs-extra": "^10.0.0",
+"highlight.js": "^10.7.2",
+"lodash": "^4.17.21",
 "markdown-it": "^8.4.2",
 "require-from-string": "^2.0.2",
-"unescape-js": "^1.1.1",
+"unescape-js": "^1.1.4",
 "vsc-leetcode-cli": "2.8.0"
 }
 }

@@ -83,7 +83,7 @@ class LeetCodeManager extends EventEmitter {
 env: createEnvOption(),
 });
 
-childProc.stdout.on("data", async (data: string | Buffer) => {
+childProc.stdout?.on("data", async (data: string | Buffer) => {
 data = data.toString();
 leetCodeChannel.append(data);
 if (data.includes("twoFactorCode")) {
@@ -96,19 +96,19 @@ class LeetCodeManager extends EventEmitter {
 childProc.kill();
 return resolve(undefined);
 }
-childProc.stdin.write(`${twoFactor}\n`);
+childProc.stdin?.write(`${twoFactor}\n`);
 }
 const successMatch: RegExpMatchArray | null = data.match(this.successRegex);
 if (successMatch && successMatch[1]) {
-childProc.stdin.end();
+childProc.stdin?.end();
 return resolve(successMatch[1]);
 } else if (data.match(this.failRegex)) {
-childProc.stdin.end();
+childProc.stdin?.end();
 return reject(new Error("Faile to login"));
 }
 });
 
-childProc.stderr.on("data", (data: string | Buffer) => leetCodeChannel.append(data.toString()));
+childProc.stderr?.on("data", (data: string | Buffer) => leetCodeChannel.append(data.toString()));
 
 childProc.on("error", reject);
 const name: string | undefined = await vscode.window.showInputBox({
@@ -120,7 +120,7 @@ class LeetCodeManager extends EventEmitter {
 childProc.kill();
 return resolve(undefined);
 }
-childProc.stdin.write(`${name}\n`);
+childProc.stdin?.write(`${name}\n`);
 const pwd: string | undefined = await vscode.window.showInputBox({
 prompt: isByCookie ? "Enter cookie" : "Enter password.",
 password: true,
@@ -131,7 +131,7 @@ class LeetCodeManager extends EventEmitter {
 childProc.kill();
 return resolve(undefined);
 }
-childProc.stdin.write(`${pwd}\n`);
+childProc.stdin?.write(`${pwd}\n`);
 });
 if (userName) {
 vscode.window.showInformationMessage(`Successfully ${inMessage}.`);

@@ -15,13 +15,13 @@ export async function executeCommand(command: string, args: string[], options: c
 
 const childProc: cp.ChildProcess = cp.spawn(command, args, { ...options, env: createEnvOption() });
 
-childProc.stdout.on("data", (data: string | Buffer) => {
+childProc.stdout?.on("data", (data: string | Buffer) => {
 data = data.toString();
 result = result.concat(data);
 leetCodeChannel.append(data);
 });
 
-childProc.stderr.on("data", (data: string | Buffer) => leetCodeChannel.append(data.toString()));
+childProc.stderr?.on("data", (data: string | Buffer) => leetCodeChannel.append(data.toString()));
 
 childProc.on("error", reject);
 
@@ -42,7 +42,7 @@ export async function executeCommand(command: string, args: string[], options: c
 export async function executeCommandWithProgress(message: string, command: string, args: string[], options: cp.SpawnOptions = { shell: true }): Promise<string> {
 let result: string = "";
 await vscode.window.withProgress({ location: vscode.ProgressLocation.Notification }, async (p: vscode.Progress<{}>) => {
-return new Promise(async (resolve: () => void, reject: (e: Error) => void): Promise<void> => {
+return new Promise<void>(async (resolve: () => void, reject: (e: Error) => void): Promise<void> => {
 p.report({ message });
 try {
 result = await executeCommand(command, args, options);

@@ -130,8 +130,6 @@ class LeetCodePreviewProvider extends LeetCodeWebview {
 
 protected onDidDisposeWebview(): void {
 super.onDidDisposeWebview();
-delete this.node;
-delete this.description;
 this.sideMode = false;
 }
 

@@ -64,7 +64,6 @@ class LeetCodeSolutionProvider extends LeetCodeWebview {
 
 protected onDidDisposeWebview(): void {
 super.onDidDisposeWebview();
-delete this.solution;
 }
 
 private parseSolution(raw: string): Solution {

@@ -59,7 +59,6 @@ class LeetCodeSubmissionProvider extends LeetCodeWebview {
 
 protected onDidDisposeWebview(): void {
 super.onDidDisposeWebview();
-delete this.result;
 }
 
 private async showKeybindingsHint(): Promise<void> {