如何检查键盘上是否释放了特定键？

Question

I want to check whether the escape key has been pressed/released in javascript.

They way I've seen is this :

document.addEventListener('keyup', function(event) {
   //returns a number for key  
  console.log(event.keyCode);   
});

However when I went onto Mozilla it says the '.keyCode' is being deprecated use '.key' instead. Which I did but when I changed the code to this:

document.addEventListener('keyup', function(event) {
   //returns a number for key  
  console.log(event.key);   
});

It wouldn't work it said in the console 'undefined'. Any ideas why?

Also is Mozilla the best place to go, because as a beginner I'm finding it difficult to understand. Thanks

Answer 1

The problem is you're adding your listener to document when it should be added to window . Eg,

window.addEventListener('keyup', function(ev) {
    console.log(ev.key);
});

Answer 2

You need to attach the event listener to the window. This may differ by browser, but it worked for me.

  window.addEventListener("keyup", function (event) { if(event.key === "Escape"){ console.log("Escape was released."); } // Consume the event for suppressing "double action". event.preventDefault(); }, true); 

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