JavaScript array deduplication: get all unique values

Question

<p>I have an array of numbers and I need to make sure the numbers in it are unique. I found the following code snippet on the internet which works fine until there is a zero in the array. I found another almost identical script on Stack Overflow, but it doesn't fail. </p>

<p>To help me learn, can anyone help me identify what's wrong with the prototype script? </p>



<pre><code>Array.prototype.getUnique = function() {
 var o = {}, a = [], i, e;
 for (i = 0; e = this[i]; i ) {o[e] = 1};
 for (e in o) {a.push (e)};
 return a;
}</code>

More answers from duplicate questions:

• Remove duplicate values ​​from JS array

Similar questions:

• Get all non-unique values ​​in the array (ie: repeated/multiple occurrences)

Answer 1

Updated answer for ES6/ES2015: One-line solution using Set and spread operator (thanks le-m) as follows:

let uniqueItems = [...new Set(items)]

The return result is:

[4, 5, 6, 3, 2, 23, 1]

Answer 2

With JavaScript 1.6 / ECMAScript 5, you can use the array's native filter method to get an array with unique values ：

function onlyUnique(value, index, array) {
  return array.indexOf(value) === index;
}

// 使用示例：
var a = ['a', 1, 'a', 2, '1'];
var unique = a.filter(onlyUnique);

console.log(unique); // ['a', 1, 2, '1']