Document common attributes and attributes collection

The last blog post said that when deleting the node information, there is a line of code document.body.removeChild (deletenode), what is document.body ? What's the relationship between body and document? Today, talk about common document properties and collection properties. The so-called document attribute refers to the single attribute information, which refers to a single object, and the collection property refers to those sub-objects within the document object that can be grouped together.

Document.title

The above code, after the page loading is complete, play an alert box out, what is the content of the surface?
Do the following to see the results
    
pops up the title content, which means that document.title points to the content of the title tag in the HTML page.
Make a breakpoint to see what else is the document property information?
Breakpoint hit alert (Document.title), line, and document monitoring

Expand the Document object to see

There are too many properties and collection properties for document, so let's take a look at these briefly.

Document.bgcolor

Like Document.bgcolor, which represents the background color, the current value is the hexadecimal representation of the #ffffff, we add a background color to the page, and then print the background color to see if the code is modified to

Pop-up box effect is

document.anchors

The properties of a collection class Document.anchors gets the collection of all the hyperlinks

Popup Box value is 3

The strange thing about this example is that the hyperlink must have the name attribute added to Document.anchors to get to the hyperlink, otherwise document.anchors gets the collection as an empty collection. If you know a friend, you can say the reason.
 document.forms
Look at a collection property document.forms get the collection of all form forms

The popup value is 2, and in the example there are two form forms.
Get a single object method in a Collection class property
And then the above code, if we want to get the id attribute value of the first form form, how to get it?
The result of a collection class property is a collection, which can be obtained by means of an array subscript,
That
var forms = Document.forms;for (i=0; i<forms.length; i++) {alert (forms[i].id);}

Next, we break down the collection properties.

You can see the item () method in which the Item method passes a parameter that is the ordinal of the object in the collection
Will alert (forms[i].id); Modified to alert (Forms.item (i). ID); The same effect.

Basically, the collection properties are accessed in both ways, and if more problems are encountered in the development, and if you want to get more access, see what you can do with the breakpoint above, and then try to find a way to start the problem.

Document common attributes and attributes collection