JavaScript The Definitive Guide 4th Edition-@Team LiB

Range.compareBoundaryPoints( )

compare positions of two ranges

Availability

DOM Level 2 Range

Synopsis

short compareBoundaryPoints(unsigned short how, 
                            Range sourceRange)
    throws DOMException;

Arguments

how: Specifies how to perform the comparison (i.e., which boundary points to compare). Legal values are the constants defined by the Range interface.
sourceRange: The range that is to be compared to this range.

Returns

-1 if the specified boundary point of this range is before the specified boundary point of sourceRange, 0 if the two specified boundary points are the same, or 1 if the specified boundary point of this range is after the specified boundary point of sourceRange.

Throws

If sourceRange represents a range of a different document than this range does, this method throws a DOMException with a code of WRONG_DOCUMENT_ERR.

Description

This method compares a boundary point of this range to a boundary point of the specified sourceRange and returns a value that specifies their relative order in the document source. The how argument specifies which boundary points of each range are to be compared. The legal values for this argument, and their meanings, are as follows:

Range.START_TO_START: Compare the start points of the two Range nodes.
Range.END_TO_END: Compare the end points of the two Range nodes.
Range.START_TO_END: Compare the start point of sourceRange to the end point of this range.
Range.END_TO_START: Compare the end point of sourceRange to the start point of this range.

The return value of this method is a number that specifies the relative position of this range to the specified sourceRange. Therefore, you might expect the range constants for the how argument to specify the boundary point for this range first and the boundary point for sourceRange second. Counterintuitively, however, the Range.START_TO_END constant specifies a comparison of the end point of this range with the start point of the specified sourceRange. Similarly, the Range.END_TO_START constant specifies a comparison of the start point of this range with the end point of the specified range.