demo小样

1.去除字符串中的空格

<div class="show-demo">
  <input class="input" />
  <pre class="pre"></pre>
  <button class="button">√</button>
</div>

  $('.input').keydown(function () {
    var v = $('.input').val();
    console.log(v);
    //TODO: trim
    v = v.replace(/\s/g, '');
    $('.pre').text(v);
  })