How to display values from array in JS?

Question

I want to display all values from array categories, but I always got [object object] or undefined. Here is code in last lines if statement, there is that problem in part between bracket [] when I want to call categories and type of categories is Object:

  const urlKeys = [...new URL(window.location.href).searchParams.keys()];

  let categories = [];

  let count = urlKeys.length;

  for (let i = 0; i < count - 1; i++) {
    categories.push({ type: paramsFromUrl.get('category' + i) })
  }  //Here I push elements in categories

  if (urlKeys[0] === 'allCategories') {
    document.getElementById('notice').innerText = "All categories included: [" + categories + "]";
    return viewsjs.createRestaurantCards(filterjs.findRestaurantsByCategory(await restaurantsjs.loadRestaurantsJSON(), categories));
  } //Here is problem

skara9 · Accepted Answer · 2021-11-29 18:31:40Z

1

categories is an array of objects. If you want to convert that to a string, you need to do JSON.stringify

"All categories included: " + JSON.stringify(categories);

If you only want to display the type and not the whole object, then:

"All categories included: [" + categories.map(obj => obj.type) + "]";

answered Nov 29, 2021 at 18:31

skara9

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1 Comment

Stephen K Over a year ago

Thank u. This works!

esqew · Accepted Answer · 2021-11-29 18:28:16Z

1

You can’t concatenate an Array directly into a String; it’s simply not the way it works. Seems like you need join(), which would return another String that you can successfully concatenate into your broader string to write into the DOM:

document.getElementById('notice').innerText = "All categories included: [" + categories.join(", ") + "]";

answered Nov 29, 2021 at 18:28

esqew

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4 Comments

Stephen K Over a year ago

Thank u, but this does not help, I still get result [object Object], [object Object],...[object Object]

skara9 Over a year ago

JS has type coersion, so it'll join automatically. It is better to explicitly declare it, but it isn't causing the problem here.

esqew Over a year ago

@StephenK Then you’ve left some critical information out of your post; what type of data is contained in categories…?

Stephen K Over a year ago

@esqew console.log(typeof (categories)) when I type this I get Object

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