纯Javascript实现ping功能的方法

function ping(ip) {
var img = new Image();
var start = new Date().getTime();
var flag = false;
var isCloseWifi = true;
var hasFinish = false;
img.onload = function() {
if ( !hasFinish ) {
flag = true;
hasFinish = true;
img.src = 'X:';
console.log('Ping ' + ip + ' success. ');
}
};
img.onerror = function() {
if ( !hasFinish ) {
if ( !isCloseWifi ) {
flag = true;
img.src = 'X:';
console.log('Ping ' + ip + ' success. ');
} else {
console.log('network is not working!');
}
hasFinish = true;
}
};
setTimeout(function(){
isCloseWifi = false;
console.log('network is working, start ping...');
},2);
img.src = 'http://' + ip + '/' + start;
var timer = setTimeout(function() {
if ( !flag ) {
hasFinish = true;
img.src = 'X://';
flag = false ;
console.log('Ping ' + ip + ' fail. ');
}
}, 1500);
}
ping('www.google.com:80');