MICROSOFT_PRESS_EBOOK_PROGRAMMING_WINDOWS_8_APPS_WITH_HTML_CSS_AND_JAVASCRIPT_PDF

Note that the productListings collection is an IMapView object and not an array; you can retrieve a
specific item in the collection by using its lookup method, as in the code above, or by using a key-based
array lookup:
var product1 = listing.productListings["product1"];
Iterating through the IMapView takes a little more work; it does not support index-based lookup nor
the foreach method. You instead use an IIterator obtained through the first method, as shown
here:
var iterator = listing.productListings.first()
var product;
while (iterator.hasCurrent) {
product = iterator.current.value;
document.getElementById(product.productId + "SellMessage").innerText =
"You can buy " + product.name + " for: " + product.formattedPrice + ".";
iterator.moveNext();
};
This code is completely equivalent to the previous snippet and relies on the fact that the product ID
just so happens to match the first part of the appropriate element ID in the HTML. In any case, this is the
sort of code you would use to present a variable list of options to the user.
In doing so, you’ll likely want to filter out those products that have already been purchased. In that
case, you’d look up the product license within the CurrentApp.licenseInformation.productLicenses
collection, which is another IMapView of ProductLicense objects, using the product’s ID as the key.
Here’s how we’d modify the code above to perform this additional step:
var iterator = listing.productListings.first()
var licenses = currentApp.licenseInformation.productLicenses;
var product, message;
while (iterator.hasCurrent) {
product = iterator.current.value;
if (licenses[product.productId].isActive) {
message = "You own " + product.name + ".";
} else {
message = "You can buy " + product.name + " for: " + product.formattedPrice + ".";
}
};
document.getElementById(product.productId + "SellMessage").innerText = message;
iterator.moveNext();
If you use this code in Scenario 2 of the sample (which is provided in the modified sample in this
chapter’s companion content), you’ll see the message “You own Product 1” when you first switch to that
scenario. You could also add a further refinement to check the expirationDate property of each
product license and display its remaining time.
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