JSFiddle - React, Tailwind, and code Playground

HTML

<input id="input" type="text" value="1234,56 €"> 
<span id="legende">Cliquer dans le champs</span>

JavaScript

$('#input').each(function(){
    this.montant = 1234.56;
}).click(function(){
    $('#legende').text('Le montant du champs + 1 = '+(this.montant+1));
});