如何合并每个数组中的值以获得一个新数组

function mergeArrays(arrays) {
  var mergedArray = [];
  for (var i = 0; i < arrays.length; i++) {
    mergedArray = mergedArray.concat(arrays[i]);
  }
  return mergedArray;
}

var arrays = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
var mergedArray = mergeArrays(arrays);
console.log(mergedArray);