Object Assign

const coba = {
    tes:{
        oke:2
    }
}

Object.assign(coba.tes, {sip:3})
coba.limit = 5
coba.order = [['sequenceOrder', 'ASC']];

// -------

const query = {
    keyword: 'coba'
}
const keywords = [];
    if (query.keyword) {
      const fields = ['header','description'];
      for (const field of fields) {
        keywords.push({
          [field]: {
            ['cek']: `%${query.keyword}%`
          }
        });
      }
    }

console.log(keywords)