web-apps/apps/common/embed/lib/util/htmlutils.js

const isIE = /msie|trident/i.test(navigator.userAgent);

var checkLocalStorage = (function () {
    try {
        var storage = window['localStorage'];
        return true;
    }
    catch(e) {
        return false;
    }
})();

if (!window.lang) {
    window.lang = (/(?:&|^)lang=([^&]+)&?/i).exec(window.location.search.substring(1));
    window.lang = window.lang ? window.lang[1] : '';
}
window.lang && (window.lang = window.lang.split(/[\-\_]/)[0].toLowerCase());

var isLangRtl = function (lang) {
    return lang.lastIndexOf('ar', 0) === 0 || lang.lastIndexOf('he', 0) === 0;
}

var ui_rtl = false;
if ( window.nativeprocvars && window.nativeprocvars.rtl !== undefined ) {
    ui_rtl = window.nativeprocvars.rtl;
} else {
    if ( isLangRtl(lang) )
        if ( checkLocalStorage && localStorage.getItem("ui-rtl") !== null )
            ui_rtl = localStorage.getItem("ui-rtl") === '1';
        else ui_rtl = true;
}

if ( ui_rtl && !isIE ) {
    document.body.setAttribute('dir', 'rtl');
    document.body.classList.add('rtl');
}
if ( isLangRtl(lang) ) {
    document.body.classList.add('rtl-font');
}
document.body.setAttribute('applang', lang);

window.isrtl = window.getComputedStyle(document.body).direction === 'rtl';