Typescript csv-parse

Question

I am trying to parse a csv file with typescript which I am totally new to. I cannot get the parser working with the correct typings.

Without typings everything is easy:

var fs = require('fs');
var parse = require('csv-parse');

var parser = parse({delimiter: ';'}, function(err, data){
  console.log(data);
});

fs.createReadStream(__dirname+'/fs_read.csv').pipe(parser);

But when it comes to typescript I get errors, I installed the typings from dt :

import * as csvParse from 'csv-parse';
import fs = require('fs');
var myParser:csvParse.CsvParser = csvParse({delimiter: ','}, function(data, err) {
  console.log(data);
});

I get the error

Type 'void | CsvParser' is not assignable to type 'CsvParser'.

Can anyone give me a hint or used csv-parse with typescript before and share their code?

what are you trying to do here csvParse({delimiter: ','}, function(data, err)....? — iberbeu
– iberbeu, Commented Sep 14, 2016 at 10:39
I want myparser to be of Type csv Parser tat implements writablestream for the last line of Code. I also tried class myparser implements csvParse.CsvParser But then I could not get the parsed data — niklas
– niklas, Commented Sep 14, 2016 at 10:44
Does this work new csvParse.CsvParse({delimiter: ','}, function(data, err).... — iberbeu
– iberbeu, Commented Sep 14, 2016 at 11:09
For anyone who is copying code from OP's question, replace parse in line 3 with parse.parse — Jerry Chin
– Jerry Chin, Commented Nov 20, 2023 at 6:12

Ross Scott · Accepted Answer · 2016-09-14 13:15:47Z

12

This is just a simple casting issue, all your code is right, its just TS needs help knowing what is being returned from CsvParse. If you take a look at the definition file, its return signature is void|parse.CsvParser. So to tell TS that it is actually a CsvParser (and not void) just cast it:

var myParser:csvParse.CsvParser = csvParse({delimiter: ','}, function(data, err) {
    console.log(data);
}) as csvParse.CsvParser;

answered Sep 14, 2016 at 13:15

Ross Scott

1,7429 silver badges16 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Pavel Petrovich · Accepted Answer · 2020-12-13 21:53:38Z

7

1. Let typescript do the work for you

Do not explain which type you want as a result of method csvParse:

var myParser = csvParse({delimiter: ','}, function(data, err) {
  console.log(data);
});

2. Use the original cast operator `<>`

var myParser:csvParse.CsvParser = <csvParse.CsvParser> csvParse({delimiter: ','}, function(data, err) {
  console.log(data);
});

Note: This only work with .ts files. In .jsx files you will see error "Expected corresponding JSX closing tag for ..."

3. Use the new operator `as`

var myParser:csvParse.CsvParser = csvParse({delimiter: ','}, function(data, err) {
  console.log(data);
}) as csvParse.CsvParser;

answered Dec 13, 2020 at 21:53

Pavel Petrovich

76411 silver badges10 bronze badges

Comments

jajones · Accepted Answer · 2018-04-13 17:33:05Z

0

I was running into a different problem and had to change the index.d.ts in @types/csv-parse from:

export = parse;

to:

export default parse;

This allowed me to access the parse function and pass it to the fs stream properly.

answered Apr 13, 2018 at 17:33

jajones

1331 silver badge5 bronze badges

Collectives™ on Stack Overflow

Typescript csv-parse

3 Answers 3

Comments

1. Let typescript do the work for you

2. Use the original cast operator `<>`

3. Use the new operator `as`

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

1. Let typescript do the work for you

2. Use the original cast operator <>

3. Use the new operator as

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related

2. Use the original cast operator `<>`

3. Use the new operator `as`