javascript event listner

 let test = document.getElementById("test");

test.addEventListener("mouseenter", function( event ) {

  

}, false);

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var item = document.getElementById("button");

item.addEventListener("mouseover", func, false);

function func()

{

}

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document.getElementById("demo").onmouseover = function() {mouseOver()};

document.getElementById("demo").onmouseout = function() {mouseOut()};

function mouseOver() {

  document.getElementById("demo").style.color = "red";

}

function mouseOut() {

  document.getElementById("demo").style.color = "black";

}

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