Pipe |

This is the documentation for Angular 6.
You can switch to the latest version Angular 7.

The result of an expression might require some transformation before you're ready to use it in a binding.

Angular pipes are a good choice for small transformations such as these. Pipes are simple functions that accept an input value and return a transformed value. They're easy to apply within template expressions, using the pipe operator (|):

Title through uppercase pipe: 
{{title | uppercase}}

You can chain expressions through multiple pipes:

Title through a pipe chain:
{{title | uppercase | lowercase}}

And you can also apply parameters to a pipe:

{{currentHero?.birthdate | date:'longDate'}}