А без JS?
<style>
.box { position:relative;}
.cont {
position:relative;
display:inline-block;
height:100px;
width:100px;
}
.layer {
position:relative;
top:0px;
left:0px;
background-color: rgba(0,0,0,0.3);
height:100%;
width:100%;
z-index:2;
}
img {
position:absolute;
top:0px;
left:0px;
height:100%;
width:100%;
z-index:1;
}
.layer:hover { background-color: rgba(0,0,0,0);}
</style>
<div class="box">
<div class="cont">
<div class="layer"></div>
<img src="https://javascript.ru/cat/list/donkey.gif">
</div>
<div class="cont">
<div class="layer"></div>
<img src="https://javascript.ru/cat/list/donkey.gif">
</div>
</div>