Regex is used with Where to search for a specified pattern in a column. For more information about regex, visit mozilla regular expression guide

JsStore

connection.select({
    from: 'Customers',
    where: {
        Country: {
            regex: /mexico|brazil/i
        }
    }
}).then(function(results) {
    //results will be array of objects.
    console.log(results);
}).catch(function(error) {
    alert(error.message);
});

Example