@@ -137,7 +137,7 @@ export function decodePacket (data, binaryType, utf8decode) {
 type = data.charAt(0);
 
 if (type === 'b') {
-return decodeBase64Packet(data.substr(1), binaryType);
+return decodeBase64Packet(data.slice(1), binaryType);
 }
 
 if (utf8decode) {
@@ -152,7 +152,7 @@ export function decodePacket (data, binaryType, utf8decode) {
 }
 
 if (data.length > 1) {
-return { type: packetslist[type], data: data.substring(1) };
+return { type: packetslist[type], data: data.slice(1) };
 } else {
 return { type: packetslist[type] };
 }
@@ -191,7 +191,7 @@ function tryDecode(data) {
 
 export function decodeBase64Packet (msg, binaryType) {
 var type = packetslist[msg.charAt(0)];
-var data = Buffer.from(msg.substr(1), 'base64');
+var data = Buffer.from(msg.slice(1), 'base64');
 if (binaryType === 'arraybuffer') {
 var abv = new Uint8Array(data.length);
 for (var i = 0; i < abv.length; i++){
@@ -305,7 +305,7 @@ export function decodePayload (data, binaryType, callback) {
 return callback(err, 0, 1);
 }
 
-msg = data.substr(i + 1, n);
+msg = data.slice(i + 1, i + 1 + n);
 
 if (length != msg.length) {
 // parser error - ignoring payload

@@ -555,7 +555,7 @@ export class Server extends BaseServer {
 return;
 }
 
-const head = Buffer.from(upgradeHead); // eslint-disable-line node/no-deprecated-api
+const head = Buffer.from(upgradeHead);
 upgradeHead = null;
 
 // delegate to ws
@@ -643,7 +643,7 @@ export class Server extends BaseServer {
 path += "/";
 
 function check(req) {
-return path === req.url.substr(0, path.length);
+return path === req.url.slice(0, path.length);
 }
 
 // cache and clean up listeners

@@ -181,7 +181,7 @@ describe("server", () => {
 .get(`http://localhost:${port}/engine.io/`)
 .query({ transport: "polling", EIO: 4 })
 .end((err, res) => {
-const sid = JSON.parse(res.text.substring(1)).sid;
+const sid = JSON.parse(res.text.slice(1)).sid;
 
 request
 .get(`http://localhost:${port}/engine.io/`)
@@ -3357,7 +3357,7 @@ describe("server", () => {
 expect(res.headers["set-cookie"].length).to.be(2);
 expect(res.headers["set-cookie"][1]).to.be("mycookie=456");
 
-const sid = JSON.parse(res.text.substring(5)).sid;
+const sid = JSON.parse(res.text.slice(5)).sid;
 
 request
 .post(`http://localhost:${port}/engine.io/`)
@@ -3394,7 +3394,7 @@ describe("server", () => {
 expect(res.headers["set-cookie"].length).to.be(2);
 expect(res.headers["set-cookie"][1]).to.be("mycookie=456");
 
-const sid = JSON.parse(res.text.substring(5)).sid;
+const sid = JSON.parse(res.text.slice(5)).sid;
 
 request
 .post(`http://localhost:${port}/engine.io/`)