findIndex() returns -1 even though item exists in the Array

Question

Here is a part of the function I'm working on:

this.instructions is an array.

I've deliberately added some console.log() just to show you that the item I'm looking for in this.instructions array exists.

insertOrUpdateI(i, instruction_frame) {

    if (i.hasOwnProperty('src_id')) {
      let iToUpdateIndex = this.instructions.findIndex(known_i => known_i.src_id == i.src_id);
      console.log('i: ',i)
      console.log('this.instructions: ',this.instructions);
      console.log('iToUpdateIndex: ', iToUpdateIndex);
      if (iToUpdateIndex > -1) {
        let oldInstruction = this.instructions[iToUpdateIndex];
        this.instructions[iToUpdateIndex] = {...i, frame: oldInstruction.frame}; // don't update the frame
        this.reconstructMatchState({
          fetchFromBack: false,
          lastFrame: this.stream.lastCameraFrame,
          applyNow: true
        }).subscribe();
        return
      }
    }
....

Here is the result I get:

i : {subject: "card", player_id: 6547, card_type: "yellow_card", src_id: 1, frame: 5077}

this.instructions: [{subject: "period", name: "period_1", start: 5031, frame: 5031, src_id: -1}, {subject: "card", player_id: 6547, card_type: "yellow_card", src_id: 1, frame: 5077}]

iToUpdateInde: -1

However, I have i.src_id === 1 and there is an item on my array that has a src_id == 1

What am I missing? I would appreciate some help!

`iToUpdateIndex = this.instructions.indexOf(i)` would work better. — , May 09 '19 at 09:48
works fine for me - https://stackblitz.com/edit/typescript-qmmf9e — CornelC, May 09 '19 at 09:48
`iToUpdateInde` indicates to me that the logs youve shown do not match tue code youve shown. [mcve] please. — Jonas Wilms, May 09 '19 at 09:50
@JonasWilms oh, my bad, I thought `findIndex` was just a typo from a copy/paste of another language. But it indeed [exists](https://developer.mozilla.org/fr/docs/Web/JavaScript/Reference/Objets_globaux/Array/findIndex) — , May 09 '19 at 09:51
@trichetriche when I do what you have suggested, my whole stops working as expected, and it doesn't work either! — yosra, May 09 '19 at 09:57
@trichetriche What about objects? `[{ foo: "bar" }].indexOf({ foo: "bar"}) == -1`. — Jack Bashford, May 09 '19 at 09:57

score 0 · Answer 1 · answered May 09 '19 at 09:55

0

Works for me here's a stackblitz example, try doing another ng serve.

answered May 09 '19 at 09:55

Ala Abid

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I did a new ng serve, and I sent 2 instructions, for the first one I got iToUpdateInde == -1 and for the second one I got iToUpdateInde == 1. – yosra May 09 '19 at 10:02
oh, that's weird, I think that should be due to an async call then! check if the instructions array or i it self is retrieved from a Http call, the first one could have failed because it was performed before response is received fromthe http call. – Ala Abid May 09 '19 at 10:07
1

try doing the console.log() before and after the findIndex() to see your data – Ala Abid May 09 '19 at 10:08
so I did the logs correspond exactly to the data I have – yosra May 09 '19 at 10:14
and still it's outputting a wrong answer? and the second findIndex() is right? strange – Ala Abid May 09 '19 at 10:16

score 0 · Answer 2 · answered May 10 '19 at 08:37

Finally, I've found an answer to my question here: Is console.log async or sync There was nothing wrong with my code, the problem may have come from the version of developer tools I was using.

It seems that console.log() have different behaviors according to the browser we're using and it's version. And sometimes it may have an asynchronous behavior, even though we aren't passing any callbacks inside of it!

findIndex() returns -1 even though item exists in the Array

2 Answers2