Error: Attempting to access the 'id' property of an undefined variable

I encountered an issue in my terminal saying:

TypeError: Cannot read properties of undefined (reading 'id')

While attempting to test the API call, this error popped up.

This is the function I am working with:

itemToForm = () => {
    this.api.send(this.component, 'get',
        { lang: 'ES', filter: { id: this.item['id'] } }
    ).then(resEsp => {
        this.item = resEsp['data'][0];
        this.api.send(this.component, 'get',
            { lang: 'EN', filter: { id: this.item['id'] } }
        ).then(res => {
            let itemEng = res['data'][0];
            let fields = this.formDef.map(register => register.filter(
                field => field['register_table'].indexOf('traduction') !== -1
            ).map(
                field => field['field_name'])
            ).filter(register => register.length);

            fields = fields.length ? fields[0] : [];

            if (itemEng) {
                this.item = Object.keys(itemEng).reduce((obj, key) => {
                    obj[key] = this.item[key];
                    if (fields.indexOf(key) !== -1) {
                        obj[key + '_eng'] = itemEng[key];
                    }
                    return obj;
                }, {});
            }

            if (this.item) {
                this.setForm();
            }
        })
    })
}

Here is my specification file:

it('should call api.send', () => {
    let spy1 = spyOn(api, 'send');
    let item = {
        id: 1,
        name: 'test',
    }

    component.addItem(item);
    component.itemToForm();

    expect(spy1).toHaveBeenCalled();
});

Answer №1

Issue at Hand:

An error occurs when the function itemToForm() is invoked before the this.item object is fully prepared.

To prevent this issue, there are various approaches that can be taken. One simple method is to include a check at the beginning of the function like so:

itemToForm = () => {
  if(this.item === undefined) {return}
         
  // Remaining code goes here
}

This effectively halts the function execution if the necessary data is not yet available.

For a more sophisticated solution, it may be beneficial to revise the order of operations and ensure that the caller of itemToForm() confirms the existence of required data prior to making the call.

Answer №2

While browsing through this thread, I stumbled upon a question that led me to realize my problem lay elsewhere.

Upon examining my code, I noticed:

import { SOME_OBJECT } from '.';

When it should have actually been:

import { SOME_OBJECT } from './proper-file';

Answer №3

While trying to install a local npm module using

npm install [path to module here]
, I encountered the issue of "Cannot read properties of undefined (reading 'spec')".

The root cause was discovered when I realized that the local module did not have a defined name in its package.json file.

Answer №4

While encountering a similar error, my solution differed since I was implementing the body-parser module within the JavaScript file.

My resolve involved incorporating:

app.use(bodyParser.urlencoded({ extended: true }));

Answer №5

Issue with Typescript version Modify the typescript version in package.json to:

"typescript": "3.8.3"

Next, run npm install

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