input框输入金额完美交互

交互内容：

输入前显示“0.00”
移入后如果是“0.00”则清空内容
移入后如果是“*.00”则去除后面的“.00”以方便填写
移入后如果是“*.*0”则优化成“*.*”，即去掉最后面的“0”以方便填写
什么都没写移出后又再次填充“0.00”
只能输入数字和小数点
仅能输入一个小数点
仅保留后面两个小数点

<div class="mui-input-row">
    <label>金额<span>(元)</span></label>
    <input type="tel" class="capital mui-input-clear" value="0.00">
</div>

<style>
*{
    font-family:'microsoft yahei';
    height:30px;
    line-height:30px;
}
input{
    width:100px;
    border-radius:.3em;
    border:1px solid #ccc;
    padding-left:.5em;
    margin-left:.3em;
}
</style>

 js部分：

/*投资本金仅能输入数字和小数点*/
var precapital;
document.querySelector('.capital').addEventListener('focus', function() {
    if (this.value == '0.00') {
        this.value = '';
    } else {
        this.value = this.value.replace(/\.00/, '').replace(/(\.\d)0/,'$1');
    }
    precapital = this.value;
});
document.querySelector('.capital').addEventListener('keyup', function() {

    this.value = this.value.replace(/^[\.]/, '').replace(/[^\d.]/g, '');
    if (this.value.split(".").length - 1 > 1) {
        this.value = precapital;
    }
    precapital = this.value;
});
document.querySelector('.capital').addEventListener('blur', function() {
    this.value = this.value.replace(/[\.]$/, '');
    this.value = this.value.replace(/(.*)\.([\d]{2})(\d*)/g,'$1.$2');
    this.value = Number(this.value).toFixed(2);
    var logNum = this.value.toString();
    if(logNum.match(/\./g) != null){
        integerNum = parseInt(logNum).toString().replace(/\d(?=(\d{3})+$)/g,'$&,');
        decimalNum = '.' + logNum.replace(/(.*)\.(.*)/g,'$2');
        document.querySelector(".logbox").innerHTML = integerNum+decimalNum;
    }else{
        document.querySelector(".logbox").innerHTML = logNum.replace(/\d(?=(\d{3})+$)/g,'$&,');
    }
});

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