提交完之后标签第一个咋会出来个undefined

let temLabels;
//先处理一下标签
console.log(this.labelList);

this.labelList.forEach((item,index)=>{
      temLabels+=item;
    console.log(temLabels);
    if (index !== this.labelList.length - 1) {
        temLabels+='-';
    }
})
this.article.labels = temLabels;