EventTarget.addEventListener(type, listener, options, useCapture)
- type
- listener
- option
- useCapture
true父传子 div > spanfalse* 子传父 span > div
document.write(`<body><div id="div">div <span id="span">span</span></div>`);
div.addEventListener('click', ()=>alert('div'))
span.addEventListener('click', ()=>alert('span'))
// "span" -> "div"
div.addEventListener('click', ()=>alert('div'), true)
span.addEventListener('click', ()=>alert('span'), true)
// "div" -> "span"
