var arr = [[1,2,3],["a","b","c"],["往","而"]]
var arc=[]
arr.forEach((item)=>{

 arc.push(...item)

})
console.log(arc)

如果僅僅是2層數(shù)據(jù)就可以用李十三的方法，如果不是，還需要擴(kuò)展進(jìn)行遍歷。

const arrays = [[1, 2], [3, 4], [5, 6]]
let newArray = arrays.reduce((a, b) => a.concat(b));
// newArray is [1, 2, 3, 4, 5, 6]

var arr = [[1,2,3],["a","b","c"],["往","而"]]
console.log(Array.prototype.concat.apply([],arr))//[1, 2, 3, "a", "b", "c", "往", "而"]

var flattened = [[0, 1], [2, 3], [4, 5]].reduce(
  function(a, b) {
    return a.concat(b);
  },
  []
);
// flattened is [0, 1, 2, 3, 4, 5]

javascript參考文檔