console
$('.imgList img').each(function (index) {
$(this).load(function () {
var ratioT = $(this).width()/$(this).height();
var ratioP = $(this).parent().width()/$(this).parent().height();
if ( ratioT <= ratioP ) {
$(this).css('width','100%');
} else {
$(this).css('height','100%');
}
})
})
<ul class="imgList">
<li><img src="https://ss0.bdstatic.com/70cFvHSh_Q1YnxGkpoWK1HF6hhy/it/u=1471875068,460028752&fm=27&gp=0.jpg"></li>
<li><img src="https://ss2.bdstatic.com/70cFvnSh_Q1YnxGkpoWK1HF6hhy/it/u=2135081425,1184147071&fm=27&gp=0.jpg"></li>
<li><img src="https://ss1.bdstatic.com/70cFuXSh_Q1YnxGkpoWK1HF6hhy/it/u=4290186613,4062719990&fm=27&gp=0.jpg"></li>
<li><img src="https://ss1.bdstatic.com/70cFvXSh_Q1YnxGkpoWK1HF6hhy/it/u=3174953969,787936730&fm=11&gp=0.jpg"></li>
<li><img src="https://ss3.bdstatic.com/70cFv8Sh_Q1YnxGkpoWK1HF6hhy/it/u=3572698774,3231888075&fm=27&gp=0.jpg"></li>
</ul>
.imgList{
display: flex;
justify-content:flex-start;
margin: 10px 0;
}
.imgList li{
width: 110px;
height: 95px;
display: flex;
justify-content: center;
align-items: center;
overflow: hidden;
margin-right: 8px;
}