JSFiddle - React, Tailwind, and code Playground
HTML
<form action="" method="post">
<input name="demo" type="text" onkeyup="this.value = this.value.replace(/[^':]*$/, '')" id="demo" />
<input type="submit" value="submit"/>
</form>
<form action="" method="post">
<input name="demo" type="text" onkeyup="this.value = this.value.replace(/[^':]*$/, '')" id="demo" />
<input type="submit" value="submit"/>
</form>