![]() ![]() We’re going setup a component which will interop with the following JavaScript function. Let’s look at an example of how we can use them to call a JavaScript function. Downcast is a powerful and highly customizable podcast app, and it separates all of the ways that you can add a podcast to your collection. Now we have covered the tools available to us. How to manually add a podcast in Downcast. How to call a JavaScript function from C# This will not work if you’re using Blazor Server. I can’t stress this enough, only use IJSInProcessRuntime when using Blazor WebAssembly. CarPlay - Fixes syncing issue when Downcast isnt running and is launched directly from CarPlay. Void InvokeVoid(string identifier, params object args) T Invoke(string identifier, params object args) This interface offers us the same two methods, only this time they are synchronous. If you have client-side only scenarios where you need to invoke a JavaScript call synchronously, then you have the ability to downcast IJSRuntime to IJSInProcessRuntime. Before Swift 5.8 that would have led to the error message, Collection downcast in cast pattern is not implemented use an explicit downcast to Dog instead. This is important because if you want your code to work in both client-side and server-side Blazor then all JS interop calls must be asynchronous due to the SignalR connection used by server-side Blazor. You’ll have noticed that both methods are async. Just as with InvokeAsync, the first argument is the function we want to call and the second allows us to pass in various arguments. Eyes downcast, maintaining little contact. The second is InvokeVoidAsync and as you can probably tell, we use this when we want to call a JavaScript function that doesn’t return anything. Its a valuable form of feedback, but it can easily be missed if youre not aware of what to look out for. If you have any parameters you need to pass to the JavaScript function, you can do so using the second argument. This identifier is relative to the window object, so if you wanted to call you would pass in ```. It takes a string, identifier, which is the identifier for the function to call. The first is InvokeAsync, we use this when we are expecting the JavaScript function we’re calling to return something to us. ValueTask InvokeVoidAsync(string identifier, params object args) ValueTask InvokeAsync(string identifier, params object args) It gives us 2 methods we can use to call JavaScript functions. This abstraction is our gateway into the JavaScript world. Because it was static it made the behaviour extremely unpredictable so the team has now removed this static implementation and developers can only use an injected instance of IJSRuntime. ![]() However, when running Blazor Server this caused some serious problems. This worked fine when using Blazor WebAssembly as the app was running in the local browser and there was no state shared with anyone else. This was a static version of the JSRuntime and avoided the need to inject anything into components or services. Historically, developers could execute their calls to JavaScript using JSRuntime.Current. JSRuntime.Static is goneīefore we go any further, I want to point out a recent change in the way JS interop works. We can even get JavaScript functions to make calls into our C# code. Future Perfect Continuous Tense He/She/It will/shall have been downcasting. ![]() The app also has features such as auto-downloading, browsing and downloading older podcast episodes, and auto-updating podcast feeds based on a schedule. You/We/They will/shall have downcast or downcasted. It allows users to search, subscribe to, and download audio and video podcasts, as well as manually subscribe to podcasts via URL. NET code alone, we can use the IJSRuntime abstraction to make calls into JavaScript functions. Downcast is a podcast app that is now available for OS X. ![]() If you’re running server-side Blazor then you don’t even have WebAssembly as an option. There are still a lot of things WebAssembly just can’t do, most notably DOM manipulation. While WebAssembly has the potential to end our reliance on JavaScript, JavaScript is not going away anytime soon. ![]()
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