问防止HTML输入中出现前导空格的正则表达式模式

EN

var noLeadingSpace = /^\w.*$/;

$("input")
  .data("oldValue", "")
  .bind("input propertychange", function() {
    var $this = $(this);
    var newValue = $this.val();

    if (!noLeadingSpace.test(newValue))
        return $this.val($this.data("oldValue"));

    return $this.data("oldValue", newValue);
  });

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

function myValidator(v){
  var input = document.getElementById('uglyWay')
  
  if(input){
    input.value = input.value.replace(/ /g, '')
  }
}

<form>
<input id="uglyWay" oninput='myValidator()' type="text" pattern="^[a-zA-Z1-9].*">
<button type="submit">Send</button>
</form>

input[type="text"]:valid{
background:green;
}
input[type="text"]:invalid{
background:red;
}

<input type="text" pattern="^[a-zA-Z1-9].*">