[ruslan_mart]

function mouseEnter() {
    this.style.color = "red";
}
 
function mouseLeave() {
    this.style.color = "black";
}


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

for(var i = 0; i < div.length; i++) {
   div[i].addEventListener('mouseenter', mouseEnter);
   div[i].addEventListener('mouseleave', mouseLeave);
}

function mouseHandler(e) {
    this.style.color = e.type === 'mouseenter' ?  'red' : 'black';
}

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

for(var i = 0; i < div.length; i++) {
   div[i].addEventListener('mouseenter', mouseHandler);
   div[i].addEventListener('mouseleave', mouseHandler);
}