How to check if a specific page is already open in Google Chrome?

Look inside the Google Mail Checker extension, which has this functionality:

function goToInbox() {  chrome.tabs.getAllInWindow(undefined, function(tabs) {    for (var i = 0, tab; tab = tabs[i]; i++) {      if (tab.url && isGmailUrl(tab.url)) {        chrome.tabs.update(tab.id, {selected: true});        return;      }    }    chrome.tabs.create({url: getGmailUrl()});  });}

In particular, you pass getAllInWindow the windowId (or undefined for the current window) and a function, which receives the array of Tab objects. You don't modify the properties of the tab directly; rather you pass its id to the update function in order to manipulate it.

To make Josh Lee's answer work using version 2 manifest, you have to add permission to the tabs in the manifest.json file:

..."permissions": [    "tabs"]...

I have no clue how this kind of construction adds 'security' to the web ...

Hope it helps the beginners!

With additional to #Josh Lee 's answer.

function openMyTab(mURL) {              if(!mURL){       console.log("No url passed");       return;    }  chrome.tabs.getAllInWindow(undefined, function(tabs) {    for (var i = 0;i<tabs.length; i++) {// remove (tabs[i].url.indexOf(mURL)!=-1) and // use tabs[i].url===url if you want exact match below      if (tabs[i].url && (tabs[i].url.indexOf(mURL)!=-1)) {        console.log("URL Match found",tabs[i].url);        chrome.tabs.update(tabs[i].id, {url:url,selected: true});        return;      }    }     console.log("URL not found. Creating new tab");    chrome.tabs.create({url: url});  });