You can get the pasted content from the paste event and the updated content of the textarea by handling the input event:
<textarea #myText (paste)="onPaste($event)" (input)="onInput(myText.value)"></textarea>
with this code:
onPaste(event: ClipboardEvent) {
let clipboardData = event.clipboardData || window.clipboardData;
let pastedText = clipboardData.getData('text');
...
}
onInput(content: string) {
...
}
See this stackblitz for a demo.