function checkFormatter(formatter, formatterName) {
        if ($.isFunction(formatter)) return true;
        if (!formatter) return false;
        throw new Error(formatterName +" must be a function or a falsy value");
    }
function checkFormatter(formatter, formatterName) {
        if ($.isFunction(formatter)) return true;
        if (!formatter) return false;
        throw new Error(formatterName +" must be a function or a falsy value");
    }
function checkFormatter ( formatter , formatterName ) { if ( $ . isFunction ( formatter ) ) return true ; if ( ! formatter ) return false ; throw new Error ( formatterName + " must be a function or a falsy value" ) ; }
Checks if the formatter function should be used.

Throws an error if it is not a function. Returns true if it should be used,
false if no formatting should be performed.

@param formatter
Checks if the formatter function should be used .