const b = [5, 2, 3, 1, 8]; var a = [], i; for (var i = 0; i < b.length; i++) { var num = b[i]; a[num] = a[num]||0; a[num] ++; num == null; } for (var i = 0; i < a.length; i++) { if(a[i]) console.log(i); }
原文：http://www.cnblogs.com/levy/p/5896142.html