1.5

there have been none yet. But if they have already been initialized, then a condition
checks if either field has changed since last time. If that's the case, then a boundary is
created through the set() method.
l Finally, the script stores the values it just read in the variables using the setVariables()
method. They will therefore become the "last values encountered" until the next event
gets fired. When called, setVariables() creates the specified variable if it doesn't already
exist and then sets the value to the second parameter passed to the function.
You can try it yourself. Paste the data into the text editor of your choice and save the file to
Albums.csv. Then create a new DataMapper configuration and load this CSV as your data file.
In the Data Input Settings, make sure you specify the first row contains field names and set the
Trigger to On script. Then paste the above JavaScript code in the Expression field and click
the Apply button to see the result.
Same basic example using a text file
So let's say we want to do the exact same thing, but this time around the Data Source is a plain
text file that looks like this:
Beatles Abbey Road 1969
Beatles Yellow Submarine 1968
Led Zeppelin Led Zeppelin 1 1969
Led Zeppelin Led Zeppelin 2 1969
Beatles Let it be 1970
Rolling Stones Let it bleed 1969
Led Zeppelin Led Zeppelin 3 1970
Led Zeppelin Led Zeppelin 4 1971
Rolling Stones Sticky Fingers 1971
Then our script would look like this:
// Read the values of both columns we want to check
var zeBand = boundaries.get(region.createRegion(1,1,30,1));
var zeYear = boundaries.get(region.createRegion(61,1,65,1));
// Check that at least one of our variables holding previous values
have been initialized already, before attempting to compare the
Page 220