XRInputSourceArray.length - Web APIs 编辑

Secure context

This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.

The read-only length property returns an integer value indicating the number of items in the input source list represented by the XRInputSourceArray object.

Syntax

let inputSourceCount = xrInputSourceArray.length;

Value

An integer value indicating the number of XRInputSource objects representing WebXR input sources are includled in the array.

Examples

In this example, a game that requires at least one input source uses length to check this before proceeding to allow the user to play the game.

let sources = xrSession.inputSources;

if (sources.length === 0) {
  showAlertDialog("You need to have at least one controller to play Super Duper Shark Jump Fest 9000.",
                  [
                    { label: "Shop Now", url: "https://www.amazon.com/s?k=vr+controllers" },
                    { label: "Quit" handler: quitGame }
                  ]);
}

Here, if length is 0, a hypothetical showAlertDialog() function is called with a prompt string explaining the need for a controller, and an array of objects, each describing a button and what should happen when it's clicked. The first takes the user to an Amazon.com search for VR controllers, and the second calls a quitGame() function to start shutting the game program down.

Specifications

Browser compatibility

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