Label 标签语句可以为一行语句添加标签，以便在复杂结构中，设置跳转目标

outerloop: //This is the label name  
for (var i=0; i < 5; i++) {  
   console.log("Outerloop: " + i);  
   innerloop:  
   
   for (var j=0; j<5; j++) {  
      if (j>3 ) break; 
      
      //Quit the innermost loop  
      if (i == 2) break innerloop; 
      
      //Do the same thing  
      if (i == 4) break outerloop; //Quit the outer loop  
      console.log("Innerloop: " + j);  
   }  
}

成功执行上述代码后，将显示以下输出。

Outerloop: 0 
Innerloop: 0 
Innerloop: 1 
Innerloop: 2 
Innerloop: 3 
Outerloop: 1 
Innerloop: 0 
Innerloop: 1 
Innerloop: 2 
Innerloop: 3 
Outerloop: 2 
Outerloop: 3 
Innerloop: 0 
Innerloop: 1 
Innerloop: 2 
Innerloop: 3 
Outerloop: 4

参考链接

https://www.learnfk.com/es6/es6-label-with-break.html