获取覆盖100% div宽度的输入标记

<div id="container">
  <input type="text" id="inputField">
</div>

#container {
  position: relative;
  width: 100%;
}

#inputField {
  position: absolute;
  width: 100%;
}

window.addEventListener('DOMContentLoaded', function() {
  var container = document.getElementById('container');
  var inputField = document.getElementById('inputField');
  
  inputField.style.width = container.offsetWidth + 'px';
});