programmers vocabulary

Sunday, March 15, 2020

Error: Cannot find module 'express'

Error Blog

Hi Guys ,

This blog is about the error Error: Cannot find module 'express'

Problem Statement

unable to run a file using node js .

Error Details

error Log

ERROR DETAILS

Error: Cannot find module 'express'
at Function.Module._resolveFilename (internal/modules/cjs/loader.js:636:15)
at Function.Module._load (internal/modules/cjs/loader.js:562:25)
at Module.require (internal/modules/cjs/loader.js:692:17)
at require (internal/modules/cjs/helpers.js:25:18)
at Object.<anonymous>
at Module._compile (internal/modules/cjs/loader.js:778:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)
at Module.load (internal/modules/cjs/loader.js:653:32)
at tryModuleLoad (internal/modules/cjs/loader.js:593:12)
at Function.Module._load (internal/modules/cjs/loader.js:585:3)

Error Code

Please validate the API endpoint .

var express = require('express');

var app = express();

app.use(express.static('public'));

app.get('/', function (req, res) {

   res.send('Hello World');

})

var server = app.listen(8082, function () {

   var host = server.address().address;

   var port = server.address().port;

   console.log("Example app listening at http://%s:%s", host, port)

})

Solution

use npm install to install the required dependencies

Code Changes

Install express

npm install express

OUTPUT

node server.js
Example app listening at http://:::8082

Thanks for reading . Let me know your thoughts in the comments below .

Friday, March 13, 2020

git cherry-pick git revert

Saturday, February 29, 2020

Uncaught (in promise) SyntaxError: Unexpected end of JSON input

Error Blog

Hi Guys ,

This blog is about the error Uncaught (in promise) SyntaxError: Unexpected end of JSON input

Problem Statement

Unable to see the response from a http call in react js .

Error Details

error Log

ERROR DETAILS

Uncaught (in promise) SyntaxError: Unexpected end of JSON input
at <anonymous>:31:28

Solution

The http call does not return a json output . .

Code Changes

Please validate the API endpoint .

componentDidMount() {

        fetch(`/api/users`)

            .then(res => res.json())

            .then(result => this.setState({ users: result.users }))

}

OUTPUT

Thanks for reading . Let me know your thoughts in the comments below .

Inline Babel script: 'this' is not allowed before super()

Error Blog

Hi Guys ,

This blog is about the error Inline Babel script: 'this' is not allowed before super()

Problem Statement

Unable to load a html page in react js .

Error Details

error Log

ERROR DETAILS

babel.min.js:4 Uncaught SyntaxError: Inline Babel script: 'this' is not allowed before super()

3 | constructor() {

4 |

> 5 | this.state = {

| ^

6 | users: []

7 | }

8 | }

at r.buildCodeFrameError (babel.min.js:4)

at e.buildCodeFrameError (babel.min.js:23)

at e.ThisExpression (babel.min.js:7)

at e.o [as _call] (babel.min.js:22)

at e.a [as call] (babel.min.js:22)

at e.l [as visit] (babel.min.js:22)

at e.visitQueue (babel.min.js:22)

at e.visitSingle (babel.min.js:22)

at e.visit (babel.min.js:22)

at Function.v.node (babel.min.js:22)

Solution

As the error suggested , we modified the code and added super before using this .

Code Changes

List of files changed

constructor() {

        super();

        this.state = {

            users: []

        }

    }

OUTPUT

Thanks for reading . Let me know your thoughts in the comments below .

Node js Web Server

Start a http server using node js .

Install http-server

npm install http-server -g

Start it

cd MyApp

http-server

Starting up http-server, serving ./
Available on:
  http://192.138.1.4:8081
  http://169.214.159.112:8081
  http://127.0.0.1:8081
Hit CTRL-C to stop the server

Open the browser and type

http://192.138.1.4:8081

You can see the index.html file being served .

In the console you will see the following output :

[Sun Mar 01 2020 13:08:41 GMT+0530 (India Standard Time)]  "GET /" "Mozilla/5.0 (Linux; Android 8.0.0; moto x4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.119 Mobile Safari/537.36"
[Sun Mar 01 2020 13:08:42 GMT+0530 (India Standard Time)]  "GET /favicon.ico" "Mozilla/5.0 (Linux; Android 8.0.0; moto x4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.119 Mobile Safari/537.36"
[Sun Mar 01 2020 13:08:42 GMT+0530 (India Standard Time)]  "GET /favicon.ico" Error (404): "Not found"
[Sun Mar 01 2020 13:08:55 GMT+0530 (India Standard Time)]  "GET /FirstApp.html" "Mozilla/5.0 (Linux; Android 8.0.0; moto x4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.119 Mobile Safari/537.36"

Thursday, February 27, 2020

crontab

Crontab is used to create a cron job

Sunday, February 23, 2020

Argument passed to when() is not a mock!

Error Blog

Hi Guys ,

This blog is about the error Argument passed to when() is not a mock! .

Problem Statement

This error will come when we try mock a class using Mockito and junit .

Error Details

error Log

ERROR DETAILS

org.mockito.exceptions.misusing.NotAMockException:

Argument passed to when() is not a mock!

Example of correct stubbing:

doThrow(new RuntimeException()).when(mock).someMethod();

at service.DbServiceTest.saveTest(DbServiceTest.java:20)

at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)

at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)

at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)

at java.lang.reflect.Method.invoke(Method.java:498)

at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)

at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)

at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)

at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)

at org.mockito.internal.runners.DefaultInternalRunner$1$1.evaluate(DefaultInternalRunner.java:44)

at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)

at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)

at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)

at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)

at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)

at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)

at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)

at org.junit.runners.ParentRunner.run(ParentRunner.java:309)

at org.mockito.internal.runners.DefaultInternalRunner$1.run(DefaultInternalRunner.java:74)

at org.mockito.internal.runners.DefaultInternalRunner.run(DefaultInternalRunner.java:80)

at org.mockito.internal.runners.StrictRunner.run(StrictRunner.java:39)

at org.mockito.junit.MockitoJUnitRunner.run(MockitoJUnitRunner.java:163)

at org.junit.runner.JUnitCore.run(JUnitCore.java:160)

at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)

at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)

at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)

at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

Solution

What made this fix

Code Changes

List of files changed

OUTPUT

Result

Thanks for reading . Let me know your thoughts in the comments below .