on keypress in javascript code example

Example 1: keypress javascript

The keypress event has been deprecated, 
you should look to use beforeinput : https://developer.mozilla.org/en-US/docs/Web/API/HTMLElement/beforeinput_event
or keydown : https://developer.mozilla.org/en-US/docs/Web/API/Document/keydown_event
instead.

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Example 2: if keypress javascript

// Create your variable and asssign it to your ID or Class in the document using document.querySelector.
let name = document.querySelector('#exampleInputEmail1');

// Now use your variable and add an event listener to it plus your keypress, event and styling
name.addEventListener("keypress", (event) => {
   name.style.border = "3px solid #28a745";
});