Home » Jquery » jQuery hasAttr checking to see if there is an attribute on an element [duplicate]

jQuery hasAttr checking to see if there is an attribute on an element [duplicate]

Posted by: admin November 2, 2017 Leave a comment

Questions:

Possible Duplicate:
Check existence of an attribute with JQuery

How do you check if there is an attribute on an element in jQuery? Similar to hasClass, but with attr?

For example,

if ($(this).hasAttr("name")) {
    // ...
}
Answers:
var attr = $(this).attr('name');

// For some browsers, `attr` is undefined; for others,
// `attr` is false.  Check for both.
if (typeof attr !== typeof undefined && attr !== false) {
    // ...
}

Questions:
Answers:

How about just $(this).is("[name]")?

The [attr] syntax is the CSS selector for an element with an attribute attr, and .is() checks if the element it is called on matches the given CSS selector.

Questions:
Answers:

If you will be checking the existence of attributes frequently, I would suggest creating a hasAttr function, to use as you hypothesized in your question:

$.fn.hasAttr = function(name) {  
   return this.attr(name) !== undefined;
};

$(document).ready(function() {
    if($('.edit').hasAttr('id')) {
        alert('true');
    } else {
        alert('false');
    }
});

<div class="edit" id="div_1">Test field</div>

Questions:
Answers:

You’re so close it’s crazy.

if($(this).attr("name"))

There’s no hasAttr but hitting an attribute by name will just return undefined if it doesn’t exist.

This is why the below works. If you remove the name attribute from #heading the second alert will fire.

Update: As per the comments, the below will ONLY work if the attribute is present AND is set to something not if the attribute is there but empty

<script type="text/javascript">
$(document).ready(function()
{
    if ($("#heading").attr("name"))
      alert('Look, this is showing because it\'s not undefined');
    else
      alert('This would be called if it were undefined or is there but empty');
});
</script>
<h1 id="heading" name="bob">Welcome!</h1>

Questions:
Answers:

Late to the party, but… why not just this.hasAttribute("name")?

Refer This

Questions:
Answers:

The best way to do this would be with filter():

$("nav>ul>li>a").filter("[data-page-id]");

It would still be nice to have .hasAttr(), but as it doesn’t exist there is this way.

Questions:
Answers:
Object.prototype.hasAttr = function(attr) {
    if(this.attr) {
        var _attr = this.attr(attr);
    } else {
        var _attr = this.getAttribute(attr);
    }
    return (typeof _attr !== "undefined" && _attr !== false && _attr !== null);      
};

I came a crossed this while writing my own function to do the same thing… I though I’d share in case someone else stumbles here.
I added null because getAttribute() will return null if the attribute does not exist.

This method will allow you to check jQuery objects and regular javascript objects.

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You can also use it with attributes such as disabled=”disabled” on the form fields etc. like so:

$("#change_password").click(function() {
    var target = $(this).attr("rel");
    if($("#" + target).attr("disabled")) {
        $("#" + target).attr("disabled", false);
    } else {
        $("#" + target).attr("disabled", true);
    }
});

The “rel” attribute stores the id of the target input field.

Questions:
Answers:

I wrote a hasAttr() plugin for jquery that will do all of this very simply, exactly as the OP has requested. More information here

EDIT:
My plugin was deleted in the great plugins.jquery.com database deletion disaster of 2010. You can look here for some info on adding it yourself, and why it hasn’t been added.