JS实现身份证输入框的输入效果

<input type="text" maxlength="8" class="idInput" onkeyup='this.value=this.value.replace(/\D/gi,"")'>

.idInput{
 width: 24.95rem;
 height: 4.7rem;
 background: url(../img/input_bg.png) center / contain no-repeat;
 font-size: 1.6rem;
 color: #1b1920;
 letter-spacing: 2.2rem; //最主要的部分，字间距
 padding-left: 1.2rem;
}