数组字转符串拼接成逗号去掉最后的逗号

	var arr=[2,3,4,5]
        var str = "";
	for (var i = 0; i < arr.length; i++) {
	  str += arr[i]+ ",";
	}
	//去掉最后一个逗号(如果不需要去掉，就不用写)
	if (str.length > 0) {
	 str = str.substr(0, str.length - 1);
	}

  或者直接判断

var arr = [2, 7, 9, 7, 9, 7];  
var str1 = "";  
for (let i = 0; i < arr.length; i++) {
      if (i < arr.length - 1) {
        str1 += arr[i] + ",";
      } else {
        str1 += arr[i];
      }
    }
//输出字符串的2,7,9,7,9,7

 拼接对象    

 for (let i = 0; i < idarr.length; i++) {
          let o = {};
          o.id = idarr[i];
          o.label = namearr[i];          
          that.toData.push(o);
    }

或者

this.TableData.forEach(item => {
	const newInfo = {
	id: item.attr id,
	lable: item.attr_vals.join(''）
	attrs.push(newInfo)
})