Microsoft script debugger for windows 10#
Microsoft script debugger code#

Microsoft script debugger code#

Once the JavaScript code has been serialized, it can be cached and loaded by the application at any point. Most but the last step can be pre-calculated ahead of time and JSRT APIs supports doing so with the JsSerializeScript function. For server scenarios in which the same code might be executed perhaps thousands of times, the performance savings this introduces can be substantial.Ĭonsider that a typical execution of a given JavaScript does an initial check for syntax errors, creates an abstract syntax tree, generates bytecode, and then starts executing the outermost scope. To support startup and execution efficiency, JSRT APIs provide the capability of pre-parsing, generating syntax trees and caching the bytecode for a given piece of JavaScript code. Startup and execution efficiency: Script Serialization Based on the app needs, hosts can provide their own threads for those operations or can force the runtime to perform those tasks on the primary thread, ensuring that applications have predictable behavior and performance characteristics. By default, each runtime manages its own set of threads for both background compilation and background garbage collection.

Chakra provides a high-performance concurrent JIT compiler and garbage collector. With JSRT APIs, hosts also get the flexibility for managing the runtime’s background operations. Such a model enables high scalability at low cost as it does not require the application to create a new thread for every request that comes in and requests need not block for other requests to be serviced. In a rental-threaded model, hosts could create thread pools to ensure that they do not exceed a particular thread (and CPU) utilization quota. Once the I/O request completes, the script context can pick any idle thread to continue script execution by using the JsSetCurrentContext API, which allows the script context to start operating again, albeit on another thread.Įach time a different thread calls JsSetCurrentContext, the script context starts executing JavaScript on a different thread. For example, the application may do some work and then decide to relinquish the thread to wait for an I/O request to complete. In other words, at any given time, script operation from one context can be executed in one thread only, but the context can change its thread affinity from time to time. In a rental threading model, a script execution context (defined here) is always single-threaded, but is not hard-bound to the thread it was created on. JSRT APIs utilize a different threading model, called rental-threading. COM tackled this problem by creating threading models and then requiring individual components to declare whether they were apartment-threaded (single-threaded) or free-threaded (any thread can interact with it), and then COM would provide automatic binding and marshaling between different threading models. However, multithreading imposes significant difficulties on the developer locks must be used in order to protect critical data structures from being corrupted. Multithreading is a common approach to improve parallelism in computing, particularly in server environments where I/O commonly causes apps to pause while waiting for an I/O request to be serviced. Threading flexibility: Rental Threading for Scalability Design Choices: Scalability, Performance and Resource ThrottlingĮver since JSRT APIs were first introduced in IE11/Windows 8.1, they have supported features that help build scalable, reliable and efficient applications and services by hosting Chakra.

Microsoft script debugger for windows 10#

For the curious, and as an example, the recently announced Node support based on Chakra for Windows 10 IoT devices is built using these APIs. These APIs now provide native access to the underlying Universal Windows Platform (UWP) and ECMAScript 6 support. Developers can now utilize these APIs to host Chakra for scripting in both Classic Windows (Win32) applications and Universal Windows applications. In Windows 10, we have made significant advancements to the JSRT APIs, making them a true first class citizen for hosting Chakra across various application types supported on Windows 10. While these APIs allowed hosting of Chakra outside the browser, the set of functionality exposed by these APIs during Windows8.1/IE11 was mainly focused on specific server side scenarios across Microsoft products and services like and Azure DocumentDB. Starting in Windows 8.1/IE11, Chakra added support for a new set of public hosting APIs called the JavaScript Runtime (JSRT) APIs, which shipped as part of the Windows SDK.

However with JavaScript’s increasing popularity in beyond-the-browser scenarios, developers have been requesting to host the Chakra engine outside the browser to enable JavaScript programmability in their native/managed applications across the client and the server. In Windows 10, the Chakra JavaScript engine powers Microsoft Edge and Windows applications written in HTML/CSS/JS.