箭头函数与this指向探究

var handler = {
    name :'handler',
    init: function() {
    let init1 = function(event) {
        console.log("init1: ", this);
        let init5 = function(){
            console.log("init5: ", this);
        }
        init5();    // init5:  Window {window: Window, self: Window, document: document, name: '', location: Location, …}
    };
    init1()    // init1:  Window {window: Window, self: Window, document: document, name: '', location: Location, …} 
    let init2 = () => console.log("init2: ", this);
    init2.call()    // init2:  {name: 'handler', init: ƒ}
    let init3 = () => {
        let init4 = ()=> console.log("init4: ", this);
        init4()    // init4:  {name: 'handler', init: ƒ}
    }
    init3.apply();
  },
};
handler.init();

printThis() {
  console.log("printThis", this);   // VueComponent {_uid: 2, _isVue: true, $options: {…}, _renderProxy: Proxy, _self: VueComponent, …}
  function print1() {
    console.log("print1: ", this);    // undefined
    function print2() {
      console.log("print2: ", this);    // undefined
      let print3 = () => void console.log("print3: ", this);    // undefined
      print3.apply()
    }
    print2.call();
    let print4 = () => void console.log("print4: ", this);    // undefined
    print4.apply();
  }
  print1.call();
  let print5 = () => {
    console.log("print5: ", this)   // VueComponent {_uid: 2, _isVue: true, $options: {…}, _renderProxy: Proxy, _self: VueComponent, …}
    let print6 = () => console.log("print6: ", this);   // VueComponent {_uid: 2, _isVue: true, $options: {…}, _renderProxy: Proxy, _self: VueComponent, …}
    print6.call();
  };
  print5();
}