js获取当前时间，返回日期yyyy-MM-dd

 1 this.now_year = new Date().getFullYear();
 2 this.now_month = new Date().getMonth() + 1;
 3 this.now_day = new Date().getDate();
 4 
 5 //now_time 当前日期
 6 let now_time ="";
 7 now_time+=this.now_year;
 8             
 9 if(this.now_month<10){
10       now_time+= '-0'+this.now_month;
11       if(this.now_day<10){
12             now_time+= '-0'+this.now_day;
13       }else{
14             now_time+= '-'+this.now_day;
15       }
16 }else{
17       now_time+='-'+ this.now_month;
18       if(this.now_day<10){
19              now_time+= '-0'+this.now_day;
20       }else{
21              now_time+= '-'+this.now_day;
22       }
23 }