var arr = []

arr.test = '测试';

arr.push(1);

arr.push(2);

arr.obj = '对象';

console.log(arr);// [ 1, 2, test: '测试', obj: '对象' ]

console.log(arr.length);// 2
console.log(arr.obj);// 对象

var arr_1 = [1,2,3];

var arr_2 = [4,5,6];

console.log(arr_1.concat(arr_2));// [1,2,3,4,5,6]