javascript, getelementbyname and focus

问题:

I am trying to create function that will look at the username if it is not valid send an alert to the user, clear the username field, and put the username field back into focus. I am trying to do this all with the getElementsBynName() function. It is all working with the exception of getting the field back into focus. My code is below. Does anyone have any suggestions.

function uchecker(uname)
{
var validUname = uname.search(/^\[e-mail]$/);
if(validUname != 0)
{
    alert("You have entered an invalid username. \n The username must be a valid @sju.edu    email    address value " + document.getElementsByName('uname')[0].value);
    document.getElementsByName('uname')[0].value = null;
    document.getElementsByName('uname')[0].focus();

    /I have also tried  document.getElementsByName('uname').focus, document.getElementsByName('uname')[0].value.focus();
}

}

So it appears that before the Java script runs the field that is in focus changes to the next field, my password input box...which also has its own validation function. I there a way to get my javascript code to run for my username field before the next textbox (password box) is takes focus?

回答1:

JavaScript:

document.getElementsByName('name')[0].focus()

Jquery:

$("#name")[0].focus()

function valid(){
  var nameObj = document.getElementsByName("testing");
  for(var i=0; i<nameObj.length; i++){
    if(nameObj[i].value == ""){
      //$(nameObj)[i].focus();  //Jquery
      nameObj[i].focus();       //Js
      alert("Please Fill all the text boxes");
      break;
    }
  }
}

<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"/>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<style>
.input-sm{
  width:200px
}
</style>
<input name="testing" class="form-control input-sm" type="text" id="test_01"/><br> 

<input name="testing" class="form-control input-sm" type="text" id="test_02"/><br>
<input name="testing" class="form-control input-sm" type="text" id="test_03"/><br>
<input name="testing" class="form-control input-sm" type="text" id="test_04"/><br>
<input type="button" class="btn btn-primary" onclick ="valid()" value="Click Me"/>

回答2:

Presumably you have controls in a form like:

<form ...>
  Username: <input type="text" name="uname" onblur="uchecker(this)">
  <span id="unameMsg"></span>
  <br>
  Password: <input type="password" name="password">
  ...
</form>

so the checker function can be:

function uchecker(element) {

  // If fail validation, show message, clear input, return focus      
  if (!/^\[e-mail]$/.test(element.value)) {
    document.getElementById(element.name + 'Msg').innerHTML = 'You have entered an invalid username. ...';
    element.value = '';
    element.focus();

  // Otherwise, clear message
  } else {
    document.getElementById(element.name + 'Msg').innerHTML = '';
  }
}

But this locks the user into completing the username field before being able to do anything else.

回答3:

I believe this might be a solution to your problem:

function onUnameFocus() {
    var uname = document.getElementsByName("uname")[0];

    uname.onblur = function () {
        var isValidUname = uname.value.search(/^\[e-mail]$/);

        if (uname.value !== "" && isValidUname) {
            uname.onblur = null;
            alert("You have entered an invalid username. \n The username must be a valid @sju.edu    email    address value " + uname.value);
            uname.value = "";
            setTimeout(function () { uname.focus(); }, 1);
        }
    }
};

<input name="uname" onfocus="onUnameFocus()" />

It sets a onfocus handle which in turn sets an onblur handle. This is been done to prevent the code from looping infinitely when it has detected an invalid username.

It also checks if the uname field is empty in order not the trap the user in there when no username has been chosen. And it adds a small delay to the focus event to ensure that it fires after the alert window has been closed.

These scripts have been tested on Chrome, Firefox and Internet Explorer 11.