js Array vs []，以及是否为空的判断

两者基本相同，唯一不同点在于初始化：

var a = [],            // these are the same
b = new Array(),   // a and b are arrays with length 0

c = [‘foo‘, ‘bar‘],           // these are the same
d = new Array(‘foo‘, ‘bar‘),  // c and d are arrays with 2 strings

// these are different:
e = [3]             // e.length == 1, e[0] == 3
f = new Array(3),   // f.length == 3, f[0] == undefined

也就是说Array(arg)，其中的arg是指生成数组的长度。

参考：What’s the difference between “Array()” and “[]” while declaring a JavaScript array?

检查array是否为空：

if (array === undefined || array.length == 0) {
    // array empty or does not exist
}