Filters out the non-unique values in an array.
Use Array.prototype.filter()
for an array containing only the unique values.
代码片段
const filterNonUnique = arr => arr.filter(i => arr.indexOf(i) === arr.lastIndexOf(i));
使用样例
filterNonUnique([1, 2, 2, 3, 4, 4, 5]); // [1, 3, 5]