console 命令行工具 X clear

console

var f1 = document.querySelector('.f1');

f1.addEventListener('mousedown', (e) => {
  console.log('down');
})
f1.addEventListener('mouseup', (e) => {
  console.log('up');
});

<div class='f1' style="color:#fff;">1</div>

.f1 {
  width: 100px;
  height: 100px;
  background: gray;
}

.red {
     background: red;
}