The approach for limiting user to single window using document cookie

SingleWindowCheckUsingCookie.js

/**
 * This function checks if multiple tabs for the application are not using the document.cookie.
 * The approach here is as follows:
 * 1. Fetch the cookies and split it and then fetch the value for the cookie name i.e. tabNumber.
 * 2. We check if the cookie is value for tabNumber is > 0, for the first time it won't be and we go to the else part
 * where we set the value to be tabNumber=1. The tab would load successfully.
 * 3. Now when we open the second tab in the same browser session, the cookie will have tabNumber=1, we extract the value
 * and we check if cookieValue > 0 and we show an alert saying second tab was opened.
 * 4. The line window.open(window.location, '_self') was added so that we get redirected using the same URL and we don't
 * let the user open the tab anyhow (my main requirement).
 * 5. The refresh of the same tab works (only 1 tab open), because in windows.onunload, we check if the cookie contains
 * tabNumber=1, if yes, we set it to 0 and as per the logic in checkForMultipleTabs, we set it to tabNumber=1 again.
 */
function checkForMultipleTab() {
    const cookies = document.cookie.split('; ');
    const row = altFind(cookies, isTab);
    let cookieValue = '0';
    if(row) {
        cookieValue = row.split('=')[1];
    }
    if(+cookieValue > 0) {
        window.alert('Only one application tab is allowed per browser session. \n' +
            'Please close this tab or the previous one.');
        window.open(window.location, '_self');
        return false;
    } else {
        document.cookie = 'tabNumber=1';
        return true;
    }
}

function isTab(row) {
    return row.indexOf('tabNumber=') === 0;
}

function altFind(arr, callback) {
    for (let i = 0; i < arr.length; i++) {
        let match = callback(arr[i]);
        if (match) {
            return arr[i];
        }
    }
}

// if(document.cookie.includes(‘tabNumber=1’)){
//     document.cookie = ‘tabNumber=0’;
// }
// This has to be added in windows.onUnload.