1.7

simply the column name. The region is passed as a parameter to the get() method, which
reads its contents and converts it into an array of strings (because any region, even a
CSV field, may contain several lines).
l To "remember" the values that were processed the last time the event was triggered, we
use variables that remain available in between events. Note that these variables are
specific to the Boundary context and not available in any other scripting context in the
DataMapper.
l The script first checks if those values were initialized. If they weren't, it means this is the
first iteration so there's no need to compare the current values with previous values since
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.
Basic example using a text file
This example is similar to the previous example, but now 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
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