一个关于jquery的Map遍历问题

Map数据结构如下:

a:["1","2"]

b:["100","200","300"]

需要得到

1 100

1  200

1 300

2 100

2 200

2 300

var need = [];
var a=[1,2];
var b=[100,200,300];
for(i=0;i<a.length;i++){
  for(j=0;j<b.length;j++){
     need.push([a[i],b[j]]);
  }
}

let a = ["1","2"]

let b = ["100","200","300"]

function combine (key,val){
  let tar =[]
  val.forEach(v=> key.forEach(k => tar.push([k,v])))
  return tar
  
}
console.log(combine(a,b))