Trying to import a class written in typescript to javascript NodeJs showing error

Question

I am creating a node express application. For my use case, I have a 1.ts file with a class as:

export class blah {
    constructor(props) {

    }
    tt() {
      console.log('logging function');
    }
}

in my 2.js file i am importing as

const blah = require('./1')
var b = new blah.blah()
console.log(b.tt())

But nothing in console.function is not being called.

How do i fix this problem. tsconfig.json file content

{
  "compilerOptions": {
    "module": "commonjs",
    "target": "es6",
   "sourceMap": true,
   "experimentalDecorators": true,
   "emitDecoratorMetadata": true
  },
 "exclude": [
"node_modules"
 ]
}

Your code works on my machine. Did you recompile with tsc 1.ts? — steven.westside
– steven.westside, Commented Feb 5, 2020 at 18:23
yes here is my package.json scripts "build-ts": "tsc && nodemon ./src/index.js", "dev": "nodemon -e ts --exec \"yarn build-ts\"" and i am running by yarn dev — Saurabh Sinha
– Saurabh Sinha, Commented Feb 5, 2020 at 18:25

abhijeet abanave · Accepted Answer · 2020-02-05 18:13:48Z

1

It must be const blah = require("./1")

answered Feb 5, 2020 at 18:13

abhijeet abanave

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4 Comments

abhijeet abanave Over a year ago

You are using {} it's used for destruction of object..means when your library export multiple things and want to access part of it then you can use destruction syntax..

Saurabh Sinha Over a year ago

no its not working with your solution, its giving the same result.

Saurabh Sinha Over a year ago

updated the question, its recognising the class but not able to call the function.

Bergi Over a year ago

Please add an explanation to your answer why you think it should look like that, and why the OP's code didn't work.

steven.westside · Accepted Answer · 2020-02-05 18:43:15Z

I am posting as an answer to post the contents of the files. This code works for me. I am running just the command tsc in the directory with the files. Output files are 1.js and 1.js.map. Then I run node 2. The output is

logging function
undefined

(On a sidenote: It prints undefined because the call console.log(b.tt()) tries to print the return value of b.tt(), but it does not return anything)

const blah = [...] gives me the same error you got.

Directory structure (everything on the same level):

1.ts
2.js
tsconfig.json

1.ts

export class blah {
    constructor(props) {

    }
    tt() {
      console.log('logging function');
    }
}

2.js

const {blah} = require('./1')
var b = new blah()
console.log(b.tt())

tsconfig.json

{
    "compilerOptions": {
        "module": "commonjs",
        "target": "es6",
        "sourceMap": true,
        "experimentalDecorators": true,
        "emitDecoratorMetadata": true
    },
    "exclude": [
        "node_modules"
    ]
}

even if i add a return statement in the function its not printing anything in the console.
Did you try just copying the contents of the files I posted and following the steps to rule out a problem with the typescript compilation? Based on if it's working or not you could rule out some possibilities for error. Maybe there is a problem with `nodemon -e ts --exec \"yarn build-ts`

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