Explain how to test if element attached to main DOM

[Enelar]

When appending DOM elements to a DocumentFragment, browsers detach them from the page. So, if you access the value of the .length property of a previously stored variable containing those elements, its value will not change, even if the elements have been detached.

Since DocumentFragment era .length do not provide accurate answer to that question in several scenarios.

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[AurelioDeRosa]

Thank you for the PR, you made a good point. I have a few suggestions to improve it.

I'd move this paragraph as the first of your PR to explain the potential issue:

When appending DOM elements to a DocumentFragment, browsers detach them from the page. So, if you access the value of the .length property of a previously stored variable containing those elements, its value will not change, even if the elements have been detached.

[AurelioDeRosa]

I was thinking that it might worth to show an example.

An example of such behavior is illustrated below:

var span = $( "span" );
var fragment = document.createDocumentFragment();

console.log( span.length ); // 1

fragment.appendChild( span.get( 0 ) );

console.log( span.length ); // Still 1!
console.log( $( "span" ).length ); // 0. The element was detached

Any thoughts?

[Enelar]

@AurelioDeRosa it may confuse if you don't use DocumentFragment directly.
(Google Chrome 54)

$('body').html('<div><a></a></div>');
var element = $('body a');
console.log(element.length); // 1
console.log(element.parents().length); // 3  div, body, html

$('body').html('');
console.log(element.length); // 1
console.log(element.parents().length); // 1 div

[AurelioDeRosa]

Hi @Enelar. I'm OK with your example too as far as we have one to clarify the concept.