[рони]

Katy93,

var mes = [[16,"Описание 1"],
    [11,"Описание 2"],
    [4,"Описание 3"],
    [0,"Описание 4"]];

var n = 12;
var title = mes.find(([a]) => n >= a);
title = title ? title[1] : 'нет описания';
alert(title);