Many objects respond to the length property accessor message. They don't all yield the same sort of value, although the value they yield will always be numeric.

For example, Window objects have a length property. In this case it will yield the number of frames in the window, and it is also available as a global variable called length.

The other objects that provide a length property don't reflect its value into so many alternative ways of accessing it. Apart perhaps from the Form.length value which is the same as the Form.elements.length value. This is necessary because the Form.elements collection is superimposed on the Form object so that you can access individual elements of the form as if they were direct member properties of the Form object. If you try to enumerate the Form object, you get lots of properties enumerated which are not form elements. You should therefore enumerate the Form.elements array.

This table lists objects which have a length property, and describes what it counts.

Although the length property is marked here as ReadOnly, in some circumstances it may be useful to assign a value to it to extend, or truncate an Array object.

Property attributes:

ReadOnly.