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• Use KRL to program a pico to serve as the "back end" to for a single page application Maintain (SPA)
• Use AJAX in the SPA to maintain state information in a the pico
• Query Use AJAX in the SPA to query for the state of a the pico

Prerequisites

You should have completed the following lessons

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In this lesson, we will build a very simple single page application which maintains start and finish times. Each measurement or timing is identified by a number (with a leading "N" or "n") and a name.

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A finished timing measurement will show, beside the starting and ending times, the elapsed time, in the format HH:MM:SS. A measurement which has started, but not yet finished, will display the starting time and a link to click when what the activity that is being measured finishes.

For our purposes, we assume that there could be multiple timekeepers, all using the application simultaneously, but that only one timekeeper will start a particular measurement. It should not be possible for timekeepers to re-use a number.

Each timekeeper who clicks on the "timing finished" link for a measurement will record a finish time, with later clicks over-writing the finish time. We'll leave it as an exercise to ignore later clicks.

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