javascrip 是否開啟多個分頁

由於 cookie 各個分頁是共用, 只要避開這一點, 就可以多開.

//the function which prevent multiple tab of same page
(function($) {
	$.fn.DuplicateWindow = function () {
		var localStorageTimeout = (5) * 1000;
		var localStorageResetInterval = (1/2) * 1000;
		var localStorageTabKey = 'my-application-browser-tab';
		var sessionStorageGuidKey = 'browser-tab-guid';

		var ItemType = {
			Session: 1,
			Local: 2
		};

		function setCookie(name, value, days) {
			var expires = "";
			if (days) {
				var date = new Date();
				date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
				expires = "; expires=" + date.toUTCString();
			}
			document.cookie = name + "=" + (value || "") + expires + "; path=/";
		}

		function getCookie(name) {
			var nameEQ = name + "=";
			var ca = document.cookie.split(';');
			for (var i = 0; i < ca.length; i++) {
				var c = ca[i];
				while (c.charAt(0) == ' ') c = c.substring(1, c.length);
				if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length, c.length);
			}
			return null;
		}

		function GetItem(itemtype) {
			var val = "";
			switch (itemtype) {
				case ItemType.Session:
					val = window.name;
					break;
				case ItemType.Local:
					val = decodeURIComponent(getCookie(localStorageTabKey));
					if (val == undefined)
						val = "";
					break;
			}
			return val;
		}

		function SetItem(itemtype, val) {
			switch (itemtype) {
				case ItemType.Session:
					window.name = val;
					break;
				case ItemType.Local:
					setCookie(localStorageTabKey, val);
					break;
			}
		}

		function createGUID() {
			this.s4 = function () {
				return Math.floor((1 + Math.random()) * 0x10000)
				  .toString(16)
				  .substring(1);
			};
			return this.s4() + this.s4() + '-' + this.s4() + '-' + this.s4() + '-' + this.s4() + '-' + this.s4() + this.s4() + this.s4();
		}

		function TestIfDuplicate() {
			var sessionGuid = GetItem(ItemType.Session) || createGUID();
			SetItem(ItemType.Session, sessionGuid);

			var val = GetItem(ItemType.Local);
			var tabObj = (val == "" ? null : JSON.parse(val)) || null;

			if (tabObj === null || (tabObj.timestamp < (new Date().getTime() - localStorageTimeout)) || tabObj.guid === sessionGuid) {
				function setTabObj() {
					var newTabObj = {
						guid: sessionGuid,
						timestamp: new Date().getTime()
					};
					SetItem(ItemType.Local, JSON.stringify(newTabObj));
				}
				setTabObj();
				setInterval(setTabObj, localStorageResetInterval);
				return false;
			}
			else {
				return true;
			}
		}

		window.IsDuplicate = function () {
			var duplicate = TestIfDuplicate();
			return duplicate;
		};

		$(window).on("beforeunload", function () {
			if (TestIfDuplicate() == false) {
				SetItem(ItemType.Local, "");
			}
		})
	}
	$(window).DuplicateWindow();
}(jQuery));

解法1:

    if(window.IsDuplicate()) {
        window.IsDuplicate = function () {return false;};
// here to trigger timer retry.
    }

解法2:

var ItemType = {
    Session: 1,
    Local: 2
};

var localStorageTabKey = 'my-application-browser-tab';
function SetItem(itemtype, val) {
 switch (itemtype) {
    case ItemType.Session:
       window.name = val;
       break;
    case ItemType.Local:
       setCookie(localStorageTabKey, val);
       break;
 }
}

function setCookie(name, value, days) {
    var expires = "";
    if (days) {
    var date = new Date();
    date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000));
    expires = "; expires=" + date.toUTCString();
    }
    document.cookie = name + "=" + (value || "") + expires + "; path=/";
}

setInterval(() => {
    SetItem(ItemType.Local, "");
}, 100);