var h2 = document.querySelectorAll('h2');

​

function nextTo(el){ // Get next sibling element

  do{el=el.nextSibling;}while(el && el.nodeType!=1);

  return el;

}

​

function toggler(){ 

  var tog = this.io ^= 1; // ^ bw. XOR

  // console.log("Toggle set to: "+ tog); // test

  // Now that we have stored 1/0 state

  // into the this.io property

  // let's do some stuff using 'tog'

  this.children[0].innerHTML = tog ? "hide" : "show";

  nextTo(this).className     = tog ? "opened" : "";

}

​

// Click event listeners to all H2 elements

for(var i=0; i<h2.length; i++){

  h2[i].addEventListener('click', toggler, false);

}

​