Why is this function definition ignored?

Question

Can anyone figure out why I get

TypeError: getStatusCode(...) is not a function

when I do?

const getStatusCode = require('./getStatusCode')
tmpStatus = await getStatusCode({url: url, timeOut: to, maxRedirects: mr})
(tmpStatus === alert['Check']['Status_code'] ) ? isOk = 1 : isOk = 0

The problem goes any if I remove the last line, where I check the value in tmpStatus.

getStatusCode.js

const axios = require('axios')
const qs = require('qs')

module.exports = async function(options) => {
  options              = options || {}
  options.url          = options.url || {}
  options.string       = options.string || null
  options.timeOut      = options.timeOut || 1000
  options.maxRedirects = options.maxRedirects || 0

  try {
    const response = await axios.get(options.url, {
      timeout: options.timeout,
      maxRedirects: options.maxRedirects,
      validateStatus: null,
      transformResponse: [function (data) {
        return data.search(options.string)
  }],
    })
    return await response.data
  } catch (error) {
    return -1
  }
}

When I run that code it throws `SyntaxError: Unexpected token '=>'` — Quentin, Aug 28 '20 at 08:52
`async function(options) =>` doesn't make sense - which kind of function are you writing? — jonrsharpe, Aug 28 '20 at 08:53
And when I fix that error, it runs fine. I can't reproduce the problem. — Quentin, Aug 28 '20 at 08:53
Does it really have `(...)` in the error message? That would happen if you added another set of parentheses: `getStatusCode({url: url, timeOut: to, maxRedirects: mr})()` — Barmar, Aug 28 '20 at 09:02
@Barmar And then it writes `TypeError: console.log(...) is not a function`. All I did were inserting your line. — Sandra Schlichting, Aug 28 '20 at 09:02
Again, that would only happen if you wrote `console.log(typeof getStatusCode)()` — Barmar, Aug 28 '20 at 09:04
If that's not what you're writing, something else is manipulating your input and adding extra function calls. — Barmar, Aug 28 '20 at 09:04
If the problem were with `getStatusCode` itself it would just say `getStatusCode is not a function`, without the `(...)` — Barmar, Aug 28 '20 at 09:05
Take a look at this [answer](https://stackoverflow.com/a/46715585/217867) and the question above it. — Lonnie Best, Aug 28 '20 at 09:06
@Barmar After some debugging. It is this line that creates the issue `(tmpStatus === alert['Check']['Status_code'] ) ? isOk = 1 : isOk = 0`, and gives the fault to the line above. What is going on here? — Sandra Schlichting, Aug 28 '20 at 09:06
Re edit: This is now a duplicate of https://stackoverflow.com/questions/2846283/what-are-the-rules-for-javascripts-automatic-semicolon-insertion-asi — Quentin, Aug 28 '20 at 09:12

score 4 · Accepted Answer · answered Aug 28 '20 at 09:11

4

The error is because you didn't put a ; at the end of the assignment line. So it's being interpreted as if you wrote

tmpStatus = await getStatusCode({url: url, timeOut: to, maxRedirects: mr})(tmpStatus === alert['Check']['Status_code'] ) 
    ? isOk = 1 : isOk = 0;

This is trying to use the result of getStatusCode() as a function, with the value of tmpStatus === alert['Check']['Status_code'] as its argument.

See What are the rules for JavaScript's automatic semicolon insertion (ASI)?

I recommend you always use semicolons, rather than depending on ASI.

answered Aug 28 '20 at 09:11

Barmar

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I had no idea that a function could return a function! When I Google `nodejs return function from function` I don't get anything meaningful. Can you give me a link where I can read about this? – Sandra Schlichting Aug 28 '20 at 09:17
1

https://davidwalsh.name/javascript-functions I found many answers by googling `javascript function returning function` – Barmar Aug 28 '20 at 09:19
`require()` is a function, and it's returning a function when you do `getStatusCode = require(...)`. So how could you be unaware that a function can return a function? – Barmar Aug 28 '20 at 09:21

score 1 · Answer 2 · answered Aug 28 '20 at 08:56

Try removing the =>.

const axios = require('axios')
const qs = require('qs')

module.exports = async function(options) {
  options              = options || {}
  options.url          = options.url || {}
  options.string       = options.string || null
  options.timeOut      = options.timeOut || 1000
  options.maxRedirects = options.maxRedirects || 0

  try {
    const response = await axios.get(options.url, {
      timeout: options.timeout,
      maxRedirects: options.maxRedirects,
      validateStatus: null,
      transformResponse: [function (data) {
        return data.search(options.string)
  }],
    })
    return await response.data
  } catch (error) {
    return -1
  }
}

I still get the same error. – Sandra Schlichting Aug 28 '20 at 08:58 — Sandra Schlichting, Aug 28 '20 at 08:58
did you restart the server before running? – elpmid Aug 28 '20 at 09:00 — elpmid, Aug 28 '20 at 09:00

Why is this function definition ignored?

2 Answers2