getTabIds = function getTabIds() {
    return this.unify(this.windowHandles(), {
        extractValue: true
    });
}
Retrieve a list of all window handles available in the session. You can use these handles to switch
to a different tab.

<example>
    :getTabIds.js
    it('should get the source of the html document', function () {
        browser.url('http://webdriver.io');

        var tabIds = browser.getTabIds();
        console.log(tabIds); // outputs: ['f9b387e0-99bd-11e6-8881-d3174a61fdce']

        browser.newWindow('http://google.com');
        tabIds = browser.getTabIds();
        console.log(tabIds); // outputs: ['f9b387e0-99bd-11e6-8881-d3174a61fdce', 'fb4e9a40-99bd-11e6-8881-d3174a61fdce' ]
    });
</example>

@alias browser.getTabIds
@return {String[]} a list of window handles
@uses protocol/windowHandles
@type window