Understanding how to bind scope in JavaScript

gistfile1.js

window.scope = "window";

Function.prototype.bind = function(scope) {
  var _function = this;
  
  return function() {
    return _function.apply(scope, arguments);
  }
}

object = {
  scope: "object",

  run: function() {
    // self-executing anonymous function with binding
    (function(word) {
      console.log(word + " " + this.scope)
    }).bind(this)("hello");

    // self-executing anonymous function without binding
    (function(word) {
      console.log(word + " " + this.scope)
    })("hello");
    
    // anonymous function with binding
    bound_af = function(word) {
      console.log(word + " " + this.scope)
    }.bind(this);
    
    bound_af("hello");

    // anonymous function without binding
    unbound_af = function(word) {
      console.log(word + " " + this.scope)
    }
    
    unbound_af("hello");
    
    // named function with binding
    function bound_nf(word) {
      console.log(word + " " + this.scope)
    }
    
    bound_nf.bind(this)("hello");

    // named function without binding
    function unbound_nf(word) {
      console.log(word + " " + this.scope)
    }
    
    unbound_nf("hello");
  }
}

object.run();