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$(function () {
    var
        elem = {
            $fontSize: $('.js-font-size'),
            $window: $(window),
        },
        params = {
            mobile: 767,
            maxHeight: 640,
            fontRatio: 98.039
        },
        changeFontSize = function () {
            var windowWith = elem.$window.width(),
                windowHeight = elem.$window.height(),
                result = windowHeight / params.fontRatio;

            if (windowWith <= params.mobile || windowHeight <= params.maxHeight) {
                return;
            }

            if (windowWith <= params.mobile ) {
                elem.$fontSize.css('fontSize', '');
                return;
            }

            elem.$fontSize.css('fontSize', result + 'px');
        };

    elem.$window.on('load resize orientationchange', changeFontSize);
});