JavaScript性能：属性的访问时间 - 'this'vs'global object'vs'variable'

var globalObject = { x: 0 }; // some global object with 'x' property

function Object()
{
    this.x = 0;
}

Object.prototype.TestPerformance = function()
{
    var xVar = 0;
}
var globalObject = { x: 0 }; // some global obj