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JS DOM FAQ

open vs visible​

接口选择 open 还是 visible 属性？

  • open - 推荐
    • open/close
    • onClose
    • 一般很少见 onOpenChange, 可能直接 onChange
  • visible
    • onVisbleChange 常见，直观
    • 但 visible 一般意味着 dom 存在、占用位置
  • dialog
    • 使用 open 属性
    • show(), showModal()
  • HTMLPopupElement
    • 使用 open 属性
    • show(), hide()
  • CSS
    • visible 占用位置
    • display:none 不占用位置
  • headlessui
    • 统一使用 open 属性
    • 传递 close 方法

query sibling​

function siblings(node, query) {
  var parent = node.parentElement;
  var index = [].slice.call(parent.children).indexOf(node) + 1;
  // nth-child 会匹配到下级
  return parent.querySelectorAll(`:nth-child(${index}) ~ ${query}`);
}

trackFocus​

const trackFocus = (p) => {
  const o = p.focus;
  p.focus = function (...args) {
    console.log(new Error().stack);
    return o.apply(this, args);
  };
};
trackFocus(HTMLElement.prototype);
trackFocus(SVGElement.prototype);

DOM 事件​

  • window
    • appinstalled
    • devicemotion, deviceorientation
    • WindowEventHandlers
      • hash, storage, online, offline, load, unload
  • document
    • afterscriptexecute, beforescriptexecute, fullscreenchange, fullscreenerror, selectionchange, visibilitychange
    • 大多事件在 window 也能监听到
  • GlobalEventHandlers
    • HTMLElement, Document, Window 都支持的事件
  • 其他
    • navigator.clipboard - cut, copy, paste
    • EventTarget 的子类

document vs body​

  • document - HTML
    • document.documentElement -> <html>
  • body
    • <body> or <frameset> or null

target vs currentTarget vs relatedTarget​

  • target - 触发事件的元素
  • currentTarget - 事件监听的元素
  • relatedTarget
    • 鼠标事件相关元素
    • 进入、离开

KeyboardEvent.key​

KeyboardEvent.code​

尽量使用 KeyboardEvent.key
  • KeyboardEvent.code
    • 忽略用户键盘布局
    • 更适用于游戏等非输入场景

Refused to set unsafe header "Content-Length"​

  • W3C XMLHttpRequest Level 1 4.6.2 定义的不允许修改的头
    • Accept-Charset
    • Accept-Encoding
    • Access-Control-Request-Headers
    • Access-Control-Request-Method
    • Connection
    • Content-Length
    • Cookie
    • Cookie2
    • Date
    • DNT
    • Expect
    • Host
    • Keep-Alive
    • Origin
    • Referer
    • TE
    • Trailer
    • Transfer-Encoding
    • Upgrade
    • User-Agent
    • Via

监听是否在当前页面​

document.addEventListener('visibilitychange', () => {
  console.log(`hidden`, document.hidden);
});
window.addEventListener('blur', () => {
  console.log(`blur`, !document.hasFocus());
});
window.addEventListener('focus', () => {
  console.log(`focus`, document.hasFocus());
});