var onglet1 = document.getElementById("onglet1");
var onglet2 = document.getElementById("onglet2");
var onglet3 = document.getElementById("onglet3");
var onglet4 = document.getElementById("onglet4");

onglet1.firstChild.style.background = "none";

var contenu1 = document.getElementById("contenu1");
var contenu2 = document.getElementById("contenu2");
var contenu3 = document.getElementById("contenu3");
var contenu4 = document.getElementById("contenu4");

contenu1.style.display="block";
contenu2.style.display="none";
contenu3.style.display="none";
contenu4.style.display="none";

function change_onglet() {
  onglet1.firstChild.style.background = 'url("./img/arrondi_corps.jpg") no-repeat left bottom';
  onglet2.firstChild.style.background = 'url("./img/arrondi_corps.jpg") no-repeat left bottom';
  onglet3.firstChild.style.background = 'url("./img/arrondi_corps.jpg") no-repeat left bottom';
  onglet4.firstChild.style.background = 'url("./img/arrondi_corps.jpg") no-repeat left bottom';
  document.getElementById(this.id).firstChild.style.background = "none";
  
  contenu1.style.display="none";
  contenu2.style.display="none";
  contenu3.style.display="none";
  contenu4.style.display="none";
  onglet_select = "contenu"+(this.id.charAt(6));
  document.getElementById(onglet_select).style.display="block";
}

onglet1.onclick=change_onglet;
onglet2.onclick=change_onglet;
onglet3.onclick=change_onglet;
onglet4.onclick=change_onglet;