How to transform a Array to a map in Javascript/Typescript

This might be an easy one but I thought it is worth saving it here.
Let's assume you want to create a HashMap in typescript or javascript with http status codes and corresponding messages. This might be useful within a frontend error handler.
Here is your error-messages.json

[


  {"code": 403,    "message": "You are not permitted to use this action."  },


  {"code": 400,    "message": "The request was incomplete or wrong."  },  


  {"code": 500,    "message": "A general error has occured."  }


]

here is how you could use it in your code:

// Map with error codes


  errorCodeMapping: Map<number, string> = new Map<number, string>();


// read error codes as json map


let array = Array.from(require("./error-messages.json"));


// map array to errorCode Map


this.errorCodeMapping = new Map(array.map((i: ErrorMessage): [number, string] => [i.code, i.message]));


// get a message for an error code


let msg: string = this.errorCodeMapping.get(403);

Karma runner Disconnected (1 times), because no message in 10000 ms.

We are using karma as the test runner within our angular 5 application. It does a pretty good job when it's time to build regression tests for our frontend. After a while using it I noticed an error during the coverage test run.

> xxxx-frontend@0.0.0 coverage C:\workspaces\andre\Intellij\xxxx\frontend
> ng test --cc --single-run
05 03 2018 08:04:47.006:INFO [karma]: Karma v2.0.0 server started at http://0.0.0.0:9876/
05 03 2018 08:04:47.009:INFO [launcher]: Launching browser Chrome with unlimited concurrency
05 03 2018 08:04:47.016:INFO [launcher]: Starting browser Chrome
05 03 2018 08:05:06.109:INFO [Chrome 64.0.3282 (Windows 7.0.0)]: Connected on socket fwQIL6cCt7q6VM0sAAAA with id 76897689
05 03 2018 08:05:12.110:WARN [Chrome 64.0.3282 (Windows 7.0.0)]: Disconnected (1 times), because no message in 6000 ms.
Chrome 64.0.3282 (Windows 7.0.0) ERROR
  Disconnected, because no message in 10000 ms.

Sometimes this happens because we got an error wihtin the test cases. After writing a lot of test cases I noticed that the execution of all test cases took about 11 sec. So I increased our timeout with setting

browserNoActivityTimeout: 60000,

within the karma.conf. That fixed the issue.