createBrowserHistory 原理

export default function createBrowserHistory() {
  const globalHistory = window.history;
  let listeners = [];
  let initialLocation = {
      pathname: window.location.pathname,
      state: globalHistory.state,//历史对象上的状态
  };
  function createHref(location) {
      return location.protocol + location.host + location.pathname + location.search + location.hash;
  }
  function setState(state) {
      Object.assign(history, state);
      history.length = globalHistory.length;
      listeners.forEach(listener => listener());
  }
  function listen(listener) {
      listeners.push(listener);//数组的push方法
  }
  function push(path, state) {
      const action = 'PUSH';
      const location = { path, state };
      globalHistory.pushState(state, null, path);
      setState({ action, location });
  }
  function go(n) {
      globalHistory.go(n);
  }
  function goBack() {
      go(-1);
  }
  function goForward() {
      go(1);
  }
  function replace(path, state) {
      const action = 'REPLACE';
      const location = { path, state };
      globalHistory.replaceState(state, null, path);
      setState({ action, location });
  }
  let isBlock;
  function block(prompt) {
      isBlock = prompt;
  }
  let history = {
      length: globalHistory.length,
      action: 'POP',//当前路径是怎么来的?
      location: initialLocation,
      createHref,//通过location对象得到一个路径字符串
      push,//跳转到新的路径里去，往历史里添加一个新条目
      replace,//跳转到新的路径里去，不会添加新的条目，而是替换当前的条目
      go,
      goBack,
      goForward,
      block,
      listen
  }
  return history;
}

https://www.yuque.com/dahai-gyz0e/tqybqc/uk76g9