Harnessing the power of VUE.js: Exploring the versatility of V-bind with Array and

I've encountered an issue with an app I'm currently working on. In my project, I am utilizing Vue.js to create the front-end and attempting to apply two classes to a div within a v-for loop.

The first class is bound with a filter that functions correctly when used independently:

v-bind:class="item.category | formatCategory"

When retrieving data from my API, the category comes in with uppercase letters and spaces. I need to clean it up by removing spaces and converting everything to lowercase. This is where my formatCategory filter comes into play:

  formatCategory: function (value) {
    if (!value) return ''
    value = value.toString()
    value = value.replace(/\s/g, '') //remove spaces
    return value.toLowerCase(); //everything in lowecase
  }
}

In addition to this, I require the class binding to display a certain class when an object is marked as completed:

v-bind:class="{completed: item.completed}"

Both of these bindings work individually, but when I try to combine them into one super component, it seems to fail:

v-bind:class="[{completed: item.completed}, item.category | formatCategory]"

Despite my efforts, I haven't been able to figure out what's going wrong after spending hours searching through Google for a solution!

<div
    class="column-object"
    v-bind:class="[{completed: item.completed}, item.category | formatCategory]"
    v-for="(item, i) in itemRows"
    v-bind:key="i"
>

Answer №1

Using filters in the incorrect manner will not work.

Quoting from the official documentation:

Vue.js provides the ability to create filters for applying common text formatting. Filters can be used within mustache interpolations and v-bind expressions (the latter introduced in version 2.1.0+). Filters need to be added at the end of the JavaScript expression and indicated by a "pipe" symbol:

The use of the vertical bar | is being misunderstood as a binary OR operation.

To address this, I recommend either creating a computed property that returns an array of classes or using your filter like a function formatCategory(item.category).

Answer №2

It might sound strange, but combining the filter function within the array-object syntax is not possible. The reason for this limitation is that Vue utilizes a regex lookbehind to extract the value and interpret it based on the $data properties of the component.

Instead, simply provide the value directly to the function since it essentially functions as a pure function:

v-bind:class="[{completed: item.completed},  formatCategory(item.category)]"

Answer №3

Aha! I managed to get it working by using this setup:

v-bind:class="[{completed: item.completed}, formatCategory(item.category)]"

I found that putting it inside a methods section did the trick for me. Now, I'm curious about understanding the distinction between a method and a computed property, so I'll be delving into that next!

methods: {
    formatCategory: function(value) {
      if (!value) return "";
      value = value.toString();
      value = value.replace(/\s/g, "");
      return value.toLowerCase();
    }
  }

Many thanks to both of you for your help!

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