JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" value="" id="tel" />
<input type="button" value="test" id="test" />
<span id='res' ></span>

JavaScript

$(function(){
regexp=/^([0-9] ?){7}[0-9]$/
    $('#test').on('click', function(){
    telnr= $('#tel').val()
    $('#res').html(regexp.test(telnr)?'bon': 'pas bon' )
    })

})