1、都是用来改变函数执行时的上下文，再具体一点就是改变函数运行时的this指向

2、区别：参数书写方式不同

call(thisObj, arg, arg2, arg3);

apply(thisObj, [args]);

bind(thisObj,arg, arg2, arg3)(); //bind 返回的是一个新的函数，必须调用它才会被执行。

Call

let p1 = {
  firstName: 'John',
  lastName: 'Smith'
};
let p2 = {
  firstName: 'Ann',
  lastName: 'Brown'
};
function sayWelcome(greeting) {
  console.log(`${greeting} ${this.firstName} ${this.lastName}`);
}
sayWelcome.call(p1, 'Welcome'); // Welcome John Smith
sayWelcome.call(p2, 'Welcome'); // Welcome Ann Brown

Apply

let p1 = {
  firstName: 'John',
  lastName: 'Smith'
};
let p2 = {
  firstName: 'Ann',
  lastName: 'Brown'
};
function sayWelcome(greeting) {
  console.log(`${greeting} ${this.firstName} ${this.lastName}`);
}
sayWelcome.apply(p1, ['Welcome']); // Welcome John Smith
sayWelcome.apply(p2, ['Welcome']); // Welcome Ann Brown

Bind

let p1 = {
  firstName: 'John',
  lastName: 'Smith'
};
let p2 = {
  firstName: 'Ann',
  lastName: 'Brown'
};
function sayWelcome(greeting,greeting2) {
  console.log(`${greeting} ${this.firstName} ${this.lastName}`)
}
sayWelcome.bind(p1, 'Welcome')(); // Welcome John Smith
sayWelcome.bind(p2, 'Welcome')(); // Welcome Ann Brown