如何将多个数组聚合为一个数组

var arr1 = [1, 2, 3];
var arr2 = [4, 5, 6];
var arr3 = [7, 8, 9];

var mergedArray = arr1.concat(arr2, arr3);
console.log(mergedArray);

var arr1 = [1, 2, 3];
var arr2 = [4, 5, 6];
var arr3 = [7, 8, 9];

var mergedArray = [...arr1, ...arr2, ...arr3];
console.log(mergedArray);

var arr1 = [1, 2, 3];
var arr2 = [4, 5, 6];
var arr3 = [7, 8, 9];

var mergedArray = [];
mergedArray.push(...arr1);
mergedArray.push(...arr2);
mergedArray.push(...arr3);
console.log(mergedArray);