how do I find an object value in a javascript array?

Question

What I want to do is check if the "content" is in my 'basket' before I add.

I tried this, but I don't understand why it's not working:

function findById(source, tag, content) {
    for (var i = 0; i < source.length; i++) {
      if (source[i].tag === content) {
        return source[i];
      }
    }
    throw "Couldn't find content ";
  }

Here is how I am using it:

var basket = {};
var tag = 'someTag';
var content = 'Joe';

const key = randomFunctions.generateRandomString(); // eg ekkciiuekks

// find out if the content is already in the basket...
var result = findById(basket, tag, content);
if(!result){
   // nope... so add it.
   basket[key] = {[tag]:content};
}

ps. I would like to keep answer in pure javascript

UPDATE

I am debugging and am getting 'undefined' when I hover over length:

source.length

ANSWER

With a slight modification to https://stackoverflow.com/users/7668258/maciej-kocik answer, this works:

function findById(source, tag, content) {
    for (let key in source) {
      let property = source[key];
      if(property[tag] === content) {
        return property[tag];
      } 
    }
    return null; // moved this OUTSIDE of for loop
  }

Can you share an example of the source object?

Camille Sébastien Niessen
– Camille Sébastien Niessen

2020-03-13 16:36:31 +00:00
Commented Mar 13, 2020 at 16:36 — Camille Sébastien Niessen
– Camille Sébastien Niessen, Commented Mar 13, 2020 at 16:36
maybe you'd like to use source[i][tag]

guijob
– guijob

2020-03-13 16:36:59 +00:00
Commented Mar 13, 2020 at 16:36 — guijob
– guijob, Commented Mar 13, 2020 at 16:36

Maciej Kocik · Accepted Answer · 2020-03-13 16:50:04Z

1

The source.length is undefined in your case. You're adding a new object property, not a new array item.

Try something like:

function findById(source, tag, content) {
  for (let key in source) {
    let property = source[key];
    if(property[tag] === content) {
      return property[tag];
    } 
    throw "Couldn't find content";
  }
}

answered Mar 13, 2020 at 16:50

Maciej Kocik

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1 Comment

MLissCetrus Over a year ago

stackoverflow.com/users/7668258/maciej-kocik - Was this a good question? did it outline all of the necessary information required for you to come up with an answer? If so, can you please up vote it? thanks

ray · Accepted Answer · 2020-03-13 16:37:20Z

0

const hasJoe = Object.values(basket).some( x => x.content === ‘Joe’);

(This isn’t quite right but I’m on my phone and editing is tricky. This is the gist of it. I’ll update when I get to a real keyboard if you don’t have an answer by then.)

answered Mar 13, 2020 at 16:37

ray

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1 Comment

ray Over a year ago

Okay. Same thing. Just turn it into a function: const hasContent = (basket, content) => Object.values(basket).some( ... )

Jasdeep Singh · Accepted Answer · 2020-03-13 16:48:55Z

0

Use for-in loop to iterate over the objects, we cannot use the traditional for loop. Please find the logic below, i have changed it according to for-in loop.

var basket = {};
var tag = 'someTag';
var content = 'Joe';

const key = randomFunctions.generateRandomString(); // eg ekkciiuekks

function findById(source, tag, content) {
  for (const property in source) {
    if (property === tag && source[property] === content) {
      return source[i];
    }
  }
  throw "Couldn't find content ";
}

// find out if the content is already in the basket...
var result = findById(basket, tag, content);
if (!result) {
  // nope... so add it.
  basket[key] = {
    [tag]: content
  };
}

answered Mar 13, 2020 at 16:48

Jasdeep Singh

8,3411 gold badge17 silver badges31 bronze badges

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