1_addEventListener.html

<!DOCTYPE html>
<html>
 <head>
  <meta charset="utf-8"/>
  <title>...</title>
  <script>
  </script>
 </head>
  
 <body>
    <button id="btnShoot">shoot</button><br>
    <button id="btnAward">获得跟踪导弹</button><br>
    <button id="btnBreak">失去跟踪导弹</button><br>
    <script>
       btnShoot.onclick=function(){
          console.log("发射普通子弹")
       }
       function show(){
             alert("发射追踪导弹=>=>=>")
          }
       btnAward.onclick=function(){
          btnShoot.addEventListener("click",show)
       }
       btnBreak.onclick=function(){
          btnShoot.removeEventListener("click",show)
       }
    </script>
 </body>
</html>