$.extend({ deepMerge: function(target, source) { for (let key in source) { if (source[key] !== null) { // null일 경우 덮어쓰지 않음 target[key] = source[key]; } } return target; }}); let a = { others: "기타사항" };let b = { others: null };let result = $.extend.deepMerge({}, a, b);console.log(result.others); // "기타사항" (b.others가 null이므로 덮어쓰지 않음)