phantomjs 测试页面加载速度

var page = require('webpage').create();
var system = require('system');
var t,url;

if(system.args.length === 1){
    console.log('Usage: app.js <some URL>');
    phantom.exit();
}else{
    t = Date.now();
    url = system.args[1];
    page.open(url,function(status){
        if(status !== 'success'){
            console.log('Failed to load the url');
        }else{
            t = Date.now() -  t;
            console.log('Page title is ' + page.evaluate(function(){
                return document.title;
            }));
            console.log('loading time ' + t + ' 毫秒');
        }
        phantom.exit();
    });
}