crosscode a promise is a promise 3 walkthrough

The example demonstrates how to wait on previous operation to be complete. The same canvas cannot be used to perform to draw two pages at the same time – The PDF.js can accept any decoded base64 data as an array. It also demonstrates how to wait until a page is loaded and rendered. The example demonstrates how promises can be used to handle errors during loading. ( function( pdf) ) Interactive examples Hello World with document load error handling var loadingTask = pdfjsLib.getDocument( 'helloworld.pdf') Remember though that PDF.js uses promises, and the above will return a PDFDocumentLoadingTask instance that has a promise property which is resolved with the document object. To get the document: pdfjsLib.getDocument( 'helloworld.pdf') From the document, more information and individual pages can be fetched. At the top level there is a document object. The object structure of PDF.js loosely follows the structure of an actual PDF. This tutorial shows how PDF.js can be used as a library in a web browser.Įxamples/ provides more examples, including usage in Node.js (at examples/node/). If promises are new to you, it’s recommended you become familiar with them before continuing on. PDF.js heavily relies on the use of Promises.

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then ( function ( result ) after property list Bad example! Spot 3 mistakes! doSomething ( ). You can capture them for analysis and handling by your code-or just to avoid having them cluttering up your output-by adding a handler for the Node.js unhandledRejection event (notice the difference in capitalization of the name), like this: One case of special usefulness: when writing code for Node.js, it's common that modules you include in your project may have unhandled rejected promises, logged to the console by the Node.js runtime.

These handlers are global per context, so all errors will go to the same event handlers, regardless of source. These make it possible to offer fallback error handling for promises, as well as to help debug issues with your promise management. In both cases, the event (of type PromiseRejectionEvent) has as members a promise property indicating the promise that was rejected, and a reason property that provides the reason given for the promise to be rejected. Sent when a promise is rejected but there is no rejection handler available. Sent when a promise is rejected, after that rejection has been handled by the executor's reject function. Promise.then() The then() method can accept two callback functions, first one executes when the Promise is resolved and the second one when Promise is rejected. Whenever a promise is rejected, one of two events is sent to the global scope (generally, this is either the window or, if being used in a web worker, it's the Worker or other worker-based interface). Now to consume the Promise we use the Promise methods like then(), catch() and finally().

Crosscode a promise is a promise 3 walkthrough