Migrate to Typescript

Created the d.ts to add TS support

Full migrate to Typescript

Reverted the change on the version

Adjusted the README.md and the example project to the Typescript version

Adjusted the README.md and the example project to the Typescript version

Merge fix

Created the d.ts to add TS support

Full migrate to Typescript

Reverted the change on the version

Adjusted the README.md and the example project to the Typescript version

Adjusted the README.md and the example project to the Typescript version

.gitignore

@@ -63,4 +63,6 @@ typings/
 # package-lock
 package-lock.json
 
-.idea
+.idea
+
+dist/

README.md

@@ -130,7 +130,7 @@ More details on how Prometheus works, you can find it [here](https://medium.com/
 In the `example` folder, you'll find a very simple but useful example to get you started. On your terminal, navigate to the project's root folder and type:
 
 ```bash
-npm i && cd example && npm i
+npm i && tsc && npm i && cd example && npm i
 ```
 
 and then

example/example.js

@@ -1,6 +1,6 @@
 const express = require("express");
 const promClient = require("prom-client");
-const Monitor = require('../lib/monitor')
+const { Monitor } = require('../dist/')
 const app = express();
 
 // inits the monitor with the express middleware to intercept the requests and register http metrics

index.js → index.ts

@@ -3,5 +3,6 @@
  * @module ExpressMonitor monitor
  */
 'use strict';
+import monitor from "./lib/monitor"
 
-exports.Monitor = require('./lib/monitor');
+export const Monitor = monitor

lib/monitor.js → lib/monitor.ts

@@ -1,7 +1,24 @@
-const promclient = require("prom-client");
+import * as promclient from "prom-client";
+import express from "express"
 
-var isCollectingMetrics = false;
-var dependencyRequestSeconds;
+let isCollectingMetrics = false;
+let dependencyRequestSeconds: promclient.Histogram;
+
+export type Monitor = {
+    init (app: express.Application, shouldCollectDefaultMetrics: boolean, buckets?: number[], version?: string, isErrorCallback?:isErrorCallback, metricsEndpoint?: string):void;
+    promclient: typeof import("prom-client");
+    watchDependencies(healthCheckCallback: HealthCheckCallback):void;
+    collectDependencyTime(request: express.Request, response: express.Response, name: string, type: "http" | "grpc" | "string"):void;
+};
+
+export type HealthCheckResult =  {
+    name: string;
+    up: boolean;
+};
+
+export type isErrorCallback = (code:number|undefined) => boolean
+export type HealthCheckCallback = (callback: HealthCheckResultCallBack) => void
+export type HealthCheckResultCallBack = (result: HealthCheckResult) => void
 
 // a gauge to observe the dependency status
 const dependencyUp = new promclient.Gauge({
@@ -19,14 +36,14 @@ const applicationInfo = new promclient.Gauge({
 /**
  * Get http response content length in bytes
  */
-function getContentLength(res) {
-    var resContentLength = "";
+function getContentLength(res: express.Response): number {
+    let resContentLength = 0;
     if ("_contentLength" in res) {
         resContentLength = res['_contentLength'];
     } else {
         // Try header
         if (res.hasHeader('content-length')) {
-            resContentLength = res.getHeader('content-length');
+            resContentLength = res.getHeader('content-length') as number;
         }
     }
     return resContentLength;
@@ -42,24 +59,24 @@ function getContentLength(res) {
  * The default isError callback for HTTP status codes. Any status 4xx and 5xx are considered errors. Other are considered success.
  * @param {string} status the HTTP status code
  */
-function defaultIsErrorCallback(status) {
-    return (/^([45].+$).*/.exec(status)) != null
+function defaultIsErrorCallback(status: number|undefined) {
+    return (/^([45].+$).*/.exec(String(status))) != null
 }
 
 /**
  * Get error message from the response. If error message is null, sets the string to empty. 
  * @param {HTTP response} res the http response
  * @returns a string with the error message or empty string if error message not found.
  */
-function getErrorMessage(res){
+function getErrorMessage(res: express.Response){
     return res.get("Error-Message") ? res.get("Error-Message") : ""
 }
 
 /**
  * Ignore query string from URL
  * @param {string} url the URL to be filtered
  */
-function filterUrl(url){
+function filterUrl(url:string){
     return url.split("?")[0]
 }
 
@@ -70,11 +87,12 @@ function filterUrl(url){
  * @param {string} name the name of dependency
  * @param {string} type which request protocol was used (e.g. http, grpc, etc)
  */
-function collectDependencyTime(req, res, name, type) {
-    end = dependencyRequestSeconds.startTimer()
-    var isErr = defaultIsErrorCallback(res.statusCode);
-    var errorMsg = getErrorMessage(res);
-    var url = filterUrl(req.originalUrl)
+function collectDependencyTime(req: express.Request, res: express.Response, name: string, type: string) {
+    const end = dependencyRequestSeconds.startTimer()
+    const isErr = defaultIsErrorCallback(res.statusCode);
+    const errorMsg = getErrorMessage(res);
+    const url = filterUrl(req.originalUrl)
+
     // observes the dependency request duration
     res.once("finish", () => {
         end({
@@ -83,7 +101,7 @@ function collectDependencyTime(req, res, name, type) {
             "status": res.statusCode,
             "method": req.method,
             "addr": url,
-            "isError": isErr,
+            "isError": String(isErr),
             "errorMessage": errorMsg
         })
     })
@@ -99,7 +117,7 @@ function collectDependencyTime(req, res, name, type) {
  * @param {?String} metricsEndpoint the endpoint where the metrics will be exposed. Defaults to /metrics.
  * @returns a PromClient to allow the addition of your custom metrics
  */
-function init(app, shouldCollectDefaultMetrics, buckets, version, isErrorCallback, metricsEndpoint) {
+function init(app: express.Application, shouldCollectDefaultMetrics?: boolean, buckets?: number[], version?: string, isErrorCallback?: isErrorCallback, metricsEndpoint?: string) {
     if (!isCollectingMetrics && app) {
         if (typeof(isErrorCallback) !== "function") {
             isErrorCallback = defaultIsErrorCallback
@@ -137,20 +155,21 @@ function init(app, shouldCollectDefaultMetrics, buckets, version, isErrorCallbac
         })
 
         // middleware to capture prometheus metrics for the request
-        app.all(/^(?!\/metrics$).*/, (req, res, next) => {
+        app.all(/^(?!\/metrics$).*/, (req: express.Request, res: express.Response, next: express.NextFunction) => {
             let end = reqSeconds.startTimer()
             next();
             res.once("finish", () => {
-                var isErr = isErrorCallback(res.statusCode);
-                var errorMsg = getErrorMessage(res);
-                var url = filterUrl(req.originalUrl);
+                const isErr = typeof isErrorCallback === "function" ? isErrorCallback(res.statusCode) : false;
+                const errorMsg = getErrorMessage(res);
+                const url = filterUrl(req.originalUrl);
+
                 // observes the request duration
                 end({
                     "type": "http",
                     "status": res.statusCode,
                     "method": req.method,
                     "addr": url,
-                    "isError": isErr,
+                    "isError": String(isErr),
                     "errorMessage": errorMsg
                 })
 
@@ -160,7 +179,7 @@ function init(app, shouldCollectDefaultMetrics, buckets, version, isErrorCallbac
                     "status": res.statusCode,
                     "method": req.method,
                     "addr": url,
-                    "isError": isErr,
+                    "isError": String(isErr),
                     "errorMessage": errorMsg
                 }, getContentLength(res))
             });
@@ -175,8 +194,9 @@ function init(app, shouldCollectDefaultMetrics, buckets, version, isErrorCallbac
             // Probe system metrics every 5th second.
             promclient.collectDefaultMetrics({timeout: 5000});
         }
-
-        applicationInfo.set({"version": version}, 1);
+        if(version){
+            applicationInfo.set({"version": version}, 1);
+        }
     }
 }
 
@@ -202,10 +222,10 @@ function init(app, shouldCollectDefaultMetrics, buckets, version, isErrorCallbac
  * Needs to return a valid array of HealthCheckResult.
  * @param {HealthCheckCallback} healthCheck
  */
-function watchDependencies(healthCheck) {
+function watchDependencies(healthCheck: HealthCheckCallback) {
     if (typeof healthCheck === 'function') {
 
-        timer = setInterval(() => {
+        setInterval(() => {
             healthCheck(registerDependencyMetrics);
         }, 15000);
 
@@ -218,12 +238,18 @@ function watchDependencies(healthCheck) {
  * Registers the current metrics for a specific dependency
  * @param {HealthCheckResult} result  the result of health checking a specific dependency
  */
-function registerDependencyMetrics(result) {
+function registerDependencyMetrics(result: HealthCheckResult): void {
     if (result) {
         dependencyUp.set({"name": result.name}, (result.up ? 1 : 0));
     }
 }
+ const m: Monitor = {
+    init,
+    promclient,
+    watchDependencies,
+    collectDependencyTime
+}
+
+export default m
+
 
-module.exports = {
-    init, promclient, watchDependencies, collectDependencyTime
-};

package.json

@@ -2,11 +2,14 @@
   "name": "@labbsr0x/express-monitor",
   "version": "2.5.0",
   "description": "A Prometheus middleware to add basic but very useful metrics for your Express JS app.",
-  "main": "index.js",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
   "directories": {
     "lib": "lib"
   },
   "scripts": {
+    "build": "tsc",
+    "prepublish": "tsc",
     "test": "echo \"Error: no test specified\" && exit 1"
   },
   "repository": {
@@ -27,5 +30,8 @@
   "dependencies": {
     "prom-client": "^11.5.3"
   },
-  "devDependencies": {}
+  "devDependencies": {
+    "@types/express": "^4.17.7",
+    "typescript": "^3.9.7"
+  }
 }

tsconfig.json

@@ -0,0 +1,17 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "target": "ES2020",
+        "noImplicitAny": true,
+        "removeComments": true,
+        "preserveConstEnums": true,
+        "esModuleInterop": true,
+        "strict": true,
+        "declaration": true,
+        "outDir": "dist"
+    },
+    "exclude": [
+        "node_modules",
+        "dist"
+    ]
+}