javascript_binding_restriction.js

function f(){
  return this.a;
}

var a = {a: 'foo'};
var b = {a: 'bar'};
var x = f.bind(a);
var y = x.bind(b);
//  bind 只能绑定一次, 可重复绑定

console.log(x());

console.log(y());

console.log(f.bind(b)());

//  foo
//  foo
//  bar