Angular Lowercase Pipe : Convert string/text to lowercase in Angular

Lower case pipe example

Angular lowercase Pipe used to convert string or text to lowercase in Angular component templates.

To convert a string to small letters in template HTML file, pass the input string to the lowercase pipe using pipe operator as shown below.

<p>{{'LOWERCASE pipe convert string to small letters in ANGULAR'
| lowercase}}</p>
<!-- Output -->
<!--lowercase pipe convert string to small letters in angular-->

It’s one of the built-in pipes in Angular and very handy pipe similar to uppercase pipe

Lowercasepipe Usage & Syntax

The syntax is very similar to other built in pipes, we need to pass input text to the lowercase pipe without any parameters.

{{ text | lowercase }}

LowerCasePipe Examples

Now We will go through the different types of strings and convert them to small case letters using Angular LowerCasePipe.

Let’s create a component called lowercasepipe in our Angular project.

ng generate component lowercasepipe 

//
CREATE src/app/lowercasepipe/lowercasepipe.component.html (28 bytes)
CREATE src/app/lowercasepipe/lowercasepipe.component.spec.ts (677 bytes)
CREATE src/app/lowercasepipe/lowercasepipe.component.ts (304 bytes)
CREATE src/app/lowercasepipe/lowercasepipe.component.scss (0 bytes)
UPDATE src/app/app.module.ts (3991 bytes)

import { Component, OnInit } from '@angular/core';

@Component({
  selector: 'app-lowercasepipe',
  templateUrl: './lowercasepipe.component.html',
  styleUrls: ['./lowercasepipe.component.scss']
})
export class LowercasepipeComponent implements OnInit {

  constructor() { }

  ngOnInit(): void {
  }

}

Convering ultra numerica string to lowercase

<p>{{'ANGULAR LOWERCASE' | lowercase}}</p>
<!-- output is "angular lowercase" --> 

<!-- Ultra numeric string to lowercase -->
<p>{{'ANGULAR version 11' | lowercase}}</p> 
<!-- output is "angular version 11" --> 

Error: InvalidPipeArgument for pipe ‘LowerCasePipe’

Angular lowercase pipe accepts only string types.

If we pass other types like number or object etc. we will get
Error: InvalidPipeArgument for pipe 'LowerCasePipe' error.

{{ 1 | lowercase}}

The above code won’t compile and angular cli returns following error

TS2345: Argument of type '1' is not assignable to parameter of type 'string'.

We will test lowercase pipe with other type variables.

export class LowercasepipeComponent implements OnInit {

id : number;
products : Product[];

constructor() { 
    this.id = 123;
    this.products = [
       {id:1,name:"product1"},
       {id:2,name:"product2"}
    ];
}

}  


interface Product{
  id: number;
  name : string;
}


In file lowercasepipe.component.html file

 {{ id | lowercase}}

And now angular cli will return error TS2345: Argument of type 'number' is not assignable to parameter of type 'string'. error when we try to compile below code.

Same with the type product

    {{ products | lowercase}}

 error TS2345: Argument of type 'Product[]' is not 
 assignable to parameter of type 'string'.

Now we will test lowercase pipe with variable of type any.

 lowercasevariable: any;

 constructor(){
   this.lowercasevariable = 1;
 }


 {{ lowercasevariable | lowercase}}

And now there will be no compile time errors and at run time we will get following error.

Error: InvalidPipeArgument: ‘1’ for pipe ‘LowerCasePipe’

If you pass object to lowercase pipe you will get following error.

I mean when we assign a object to variable type of any.

Error: InvalidPipeArgument: ‘[object Object]’ for pipe ‘LowerCasePipe’

If you assign string to any type variable lowercase pipe will work as expected.

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