Javascript – the difference between removeProp and removeAttr in JQuery 1.6


If you removeProp on something you should have used removeAttr() on will it silently fail? Will it work? Will it actually remove the entire attribute or just the value inside it?

If checked is added using removeProp(), can it be removed with removeAttr()?

Many questions!

Best Solution

The official jQuery blog provides a very clear explanation:

In the 1.6 release we’ve split apart the handling of DOM attributes and DOM properties into separate methods. The new .prop() method sets or gets properties on DOM elements, and .removeProp() removes properties. In the past, jQuery has not drawn a clear line between properties and attributes. Generally, DOM attributes represent the state of DOM information as retrieved from the document, such as the value attribute in the markup . DOM properties represent the dynamic state of the document; for example if the user clicks in the input element above and types def the .prop("value") is abcdef but the .attr("value") remains abc.

In most cases, the browser treats the attribute value as the starting value for the property, but Boolean attributes such as checked or disabled have unusual semantics.

For example, consider the markup <input type="checkbox" checked>. The presence of the checked attribute means that the DOM .checked property is true, even though the attribute does not have a value. In the code above, the checked attribute value is an empty string (or undefined if no attribute was specified) but the checked property value is true.

Before jQuery 1.6, .attr("checked") returned the Boolean property value (true) but as of jQuery 1.6 it returns the actual value of the attribute (an empty string), which doesn’t change when the user clicks the checkbox to change its state.

There are several alternatives for checking the currently-checked state of a checkbox. The best and most performant is to use the DOM property directly, as in this.checked inside an event handler when this references the element that was clicked. In code that uses jQuery 1.6 or newer, the new method $(this).prop("checked") retrieves the same value as this.checked and is relatively fast. Finally, the expression $(this).is(":checked") works for all versions of jQuery.