限制文本输入中小数后的位数

var myInput = document.querySelector('#fixed2');
myInput.addEventListener("keyup", function(){
  myInput.value = myInput.value.replace(/(\.\d{2})\d+/g, '$1');
});

<input id="fixed2" type="text" />

var myInputs = document.querySelectorAll('.fixed');
myInputs.forEach(function(elem) {
  elem.addEventListener("input", function() {
    var dec = elem.getAttribute('decimals');
    var regex = new RegExp("(\\.\\d{" + dec + "})\\d+", "g");
    elem.value = elem.value.replace(regex, '$1');
  });
});

<input class="fixed" type="text" decimals="2" placeholder="2 decimals only" />
<br><br>
<input class="fixed" type="text" decimals="3" placeholder="3 decimals only" />

$(document).ready(function() {
  $("input").on("blur", function() {
    $(this).val(parseFloat($(this).val()).toFixed(2));
  })
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="number" step="0.01" min="0" />