webview页面和壳通信的库（精简版）

// PG精简版
(function() {
var PG = {
iosBridge: null,
callbackId: 0,
callbacks: [],
commandQueue: [],
commandQueueFlushing: false
},
ua = navigator.userAgent,
isIOS = (ua.indexOf("iPhone") > -1 || ua.indexOf("iPad") > -1 || ua.indexOf("iPod") > -1) ? true : false;
PG.getAndClearQueuedCommands = function () {
var commandQueue_json = JSON.stringify(PG.commandQueue);
PG.commandQueue = [];
return commandQueue_json;
};

PG.exec = function(method, callback, args) {
var callbackId = '';
if (typeof(callback) == "undefined") {
callback = null;
}
if (typeof(args) == "undefined") {
args = {};
}

if (callback && typeof(callback) == 'function') {
callbackId = method + PG.callbackId++;
PG.callbacks[callbackId] = callback;
}

var obj = {
Method: method,
CallbackId: callbackId,
Args: args
};

if (isIOS) {
if (PG.iosBridge == null) {
PG.iosBridge = document.createElement("iframe");
PG.iosBridge.setAttribute("style", "display:none;");
PG.iosBridge.setAttribute("height", "0px");
PG.iosBridge.setAttribute("width", "0px");
PG.iosBridge.setAttribute("frameborder", "0");
document.documentElement.appendChild(PG.iosBridge);
}

PG.commandQueue.push(JSON.stringify(obj));
if (!PG.commandQueueFlushing) {
PG.iosBridge.src = 'pg://ready';
}

} else if (window.comjs) {
// android
window.comjs.notify('pg://' + encodeURIComponent(JSON.stringify(obj)));
} else {
console.log("非ios或android平台，不合适吧");
}

};

PG.callback = function(callbackId, args) {
if (PG.callbacks[callbackId]) {
try {
var temp = decodeURIComponent(args),
obj = JSON.parse(temp);

PG.callbacks[callbackId](obj);

} catch (e) {
console.log("Error in success callback: " + callbackId + " = " + e);
}

delete PG.callbacks[callbackId];

}
};

if (typeof(window) === "object" && typeof(window.document) === "object") {
window.PG = PG;
}

})();