The Angular KeyValue Pipe: Easily Display Key-Value Pairs in Your UI

In Angular, we often need to display data in our UI in a way that’s easy for users to understand. An example of this might be displaying a list of key-value pairs, like a dictionary or a set of configuration options. Fortunately, Angular provides us with a simple and powerful way to accomplish this: the KeyValue pipe.

What is the KeyValue Pipe?

The KeyValue pipe is an Angular built-in pipe that allows us to iterate over an object’s properties and display them in a key-value format, with each key-value pair separated by a separator and each pair separated by a delimiter.

How to use KeyValue Pipe

Using the KeyValue pipe is simple. First, let’s assume we have an object and we want to display its properties in a key-value format. We can use the KeyValue pipe in our template like so:

“`html

“`

Here, we’re using an ngFor loop to iterate over each property in myObject. We’re then using the KeyValue pipe to convert each property into a key-value pair, which we can then display in our template using {{item.key}} and {{item.value}}.

Custom Delimiters and Separators

By default, the KeyValue pipe separates each key-value pair with a comma and a space (, ), and each pair with a line break (\n). However, we can customize these delimiters and separators using the optional parameters of the pipe.

In the following example, we customize the delimiters and separators to use a semicolon (;) as the delimiter and a dash (-) as the separator:

“`html

“`

Now, each pair in our list will be separated by a semicolon, and each key-value pair will be separated by a dash.

FAQs

1. Can the KeyValue pipe handle nested objects?

No, the KeyValue pipe only works on flat objects, so it won’t work on nested objects.

2. Can I use the KeyValue pipe with arrays?

The KeyValue pipe only works with objects, so it can’t be used directly with arrays. However, you can use the KeyValue pipe with objects that have array properties. Here’s an example:

“`html

“`

Here, we’re using an ngIf statement to check if the value of each property is an array. If so, we’re displaying the array as an unordered list using another ngFor loop.

3. How can I sort the key-value pairs in my list?

The KeyValue pipe doesn’t support sorting by default, but you can accomplish this by writing a custom pipe. Here’s an example:

“`javascript
import { Pipe, PipeTransform } from ‘@angular/core’;

@Pipe({name: ‘sortKeyValue’})
export class SortKeyValuePipe implements PipeTransform {
transform(value: any, args?: any): any[] {
const sortedKeys = Object.keys(value).sort();
return sortedKeys.map(key => ({key: key, value: value[key]}));
}
}
“`

Here, we’re creating a custom pipe called sortKeyValue, which takes an object as input and returns its properties sorted alphabetically. We then map over the sorted keys to create an array of key-value pairs, which we can then display using the KeyValue pipe.

In our template, we can use the custom pipe like so:

“`html

“`

Now, our list will display the key-value pairs in alphabetic order.