为什么在console.log 中不能显示keyCode？

Question

I want to show all keyCodes when you type some characters in the input tag. ob is the input ,bind a function checkWord with event onkeydown , why console.log can't show its keycode value?

 ob = window.document.getElementById("check"); function checkWord(){ console.log(onkeydown.keyCode); } ob.addEventListener("onkeydown",checkWord);

 <input id="check" type="text">

I want console.log to show 65 when I type a in the input tag.

Answer 1

Hmm you can do it like that:

 // Getting Element const textInput = document.getElementById("textInput"); // Adding event listener textInput.addEventListener("keyup", event => { console.log(event.keyCode); });

 <input type="text" id="textInput">

In your code it would look like this:

 const ob = document.getElementById("check"); ob.addEventListener("keydown",checkWord); function checkWord(event){ console.log(event.keyCode); }

 <input type="text" id="check">

This mainly did not work because you did use the wrong event name ( onkeydown -> keydown ) and you didn't pass the event to your function.

BTW: onkeydown exists but is used like that:

object.onkeydown = function;

The difference between onkeydown and addEventLisener is that onkeydown is being defined once and with the event listeners you can add as meany to the same event as you want.

// Adds listener
object.onkeydown = function0;
// Overwrites the old listener
object.onkeydown = function1;

// Add listener
object.addEventLisener("keydown", function0);
// Add another listener to the stack
object.addEventLisener("keydown", function1);

Answer 2

You have two issues

• The event is named keydown .
• keyCode is a property of the event that get's passed to your handler

 ob = window.document.getElementById("check"); function checkWord(e){ console.log(e.keyCode); } ob.addEventListener("keydown",checkWord);

 <input id="check" />