call内部实现

Function.prototype.call = function(context){context.fn = this//获取函数执行的参数let args = [...arguments].slice(1)let res = context.fn(...args)delete context.fnreturn res
}

apply内部实现

Function.prototype.apply= function(context){context.fn = this//获取函数执行的参数数组let args = arguments[1]let res = context.fn(...args)delete context.fnreturn res
}

bind内部实现

Function.prototype.myBind= function(context){context.fn = this//获取函数执行的参数let args = [...arguments].slice(1)return function(){let newArgs = args.concat([...arguments])let res = context.fn(...newArgs)delete context.fnreturn res}	
}