angular key value pipe compareFn example

Angular KeyValue Pipe CompareFn Example

When working with Angular, we often need to manipulate data in various ways, including sorting and filtering. The Angular KeyValue pipe is a useful tool for sorting and filtering data based on key-value pairs.

One of the features of the KeyValue pipe is the ability to provide a compare function to determine the order of the items in the output. By default, the KeyValue pipe sorts based on the keys of the input object. However, we may want to sort based on the values or on some other custom logic.

Example

Suppose we have an object of fruits and their quantities:

fruits = {apple: 10, banana: 5, orange: 20}

We want to sort the fruits based on their quantity in descending order. To do this, we can use the KeyValue pipe with a custom compare function:

<div *ngFor="let fruit of fruits | keyvalue: sortByQuantity">
  {{fruit.key}}: {{fruit.value}}
</div>

sortByQuantity(a: KeyValue<string, any>, b: KeyValue<string, any>): number {
  return b.value - a.value;
}

In this example, we define a function called sortByQuantity that takes two parameters of type KeyValue. The function returns a number that represents the order of the two items.

The function simply subtracts the value of b from the value of a, which sorts in descending order. If we wanted to sort in ascending order, we would swap a and b in the function.

We then use the KeyValue pipe in our ngFor loop and pass in the sortByQuantity function as the compare function.

And that's how you can use the Angular KeyValue Pipe CompareFn Example to easily sort and display data in your Angular app.