forloop.js

var arr1 = [1, 2, 3, 4];
var arr2 = [7, 8, 9, 1];

loop1: for (let element1 of arr1) {//define a breakpoint
  for (let element2 of arr2) {
    console.log(element1, " ", element2);

    if (element1 === element2) {
      console.log("duplicate numbers");
      break loop1;//if a specific condition is met , break the loop
    }
  }
}