给数组里面的数据添加一组新数据

data.data.forEach((item,index) => {
                    console.log(item.excerpt.length)
                    let excerpt3 = {excerpt2:''};
                    let newObj
                  if(item.excerpt.length > 120){
                    excerpt3.excerpt2 = item.excerpt.slice(0,120);
                    newObj =  Object.assign(item,excerpt3);
                    // this.DataList[index].excerpt2 = excerpt2;
                    console.log(newObj)
                    this.DataList.push(newObj);

                  }
                });