Can't check nested object variables in a single line

Question

I need to show a welcome-modal to user on his first time to that page.

This code works fine:

if(this.app_data) {
  if(this.app_data['company']){
    if(this.app_data['company']['welcomed'] === false){
      this.openWelcomeModal();
    }
  }
}

The problem is the messy code checking nested variable structure.

The clear way to do it would be use a single line like this:

if(this.app_data['company']['welcomed'] === false){
  this.openWelcomeModal();
}

But this generates error:

    core.js:7376 ERROR TypeError: Cannot read properties of undefined (reading 'welcomed')
        at SafeSubscriber._next (game.page.ts:46:39)

Is there any way to do it in a single line, without need to check each level of nested object?

Does this answer your question? [Test for existence of nested JavaScript object key](https://stackoverflow.com/questions/2631001/test-for-existence-of-nested-javascript-object-key) — Heretic Monkey, Jan 03 '23 at 20:20

score 5 · Accepted Answer · answered Jan 03 '23 at 20:14

5

Optional chaining to the rescue!

if(this.app_data?.['company']?.['welcomed'] === false){
  this.openWelcomeModal();
}

answered Jan 03 '23 at 20:14

nate-kumar

1,675
2
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15

this generates compile error on dots `error TS1109: Expression expected.`... i'm only able to use this syntax without error on template parsing. – anderlaini Jan 03 '23 at 20:17
The syntax above is valid, check this TypeScript playground: https://tsplay.dev/mAd1RN. You may have another syntax issue in your code? – nate-kumar Jan 03 '23 at 20:21
2

@anderlaini Please [edit] your question to show a [mre] that displays the error you are encountering. – Heretic Monkey Jan 03 '23 at 20:22

Can't check nested object variables in a single line

1 Answers1