Create an iterator which returns unique values.

Usage no npm install needed!

<script type="module">
  import stdlibIterUnique from 'https://cdn.skypack.dev/@stdlib/iter-unique';



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Create an iterator which returns unique values.


npm install @stdlib/iter-unique


var iterUnique = require( '@stdlib/iter-unique' );

iterUnique( iterator )

Returns an iterator which returns unique values.

var array2iterator = require( '@stdlib/array-to-iterator' );

var it = iterUnique( array2iterator( [ 2, 1, 1, 2, 4, 3, 4, 3 ] ) );
// returns <Object>

var v = it.next().value;
// returns 2

v = it.next().value;
// returns 1

v = it.next().value;
// returns 4

v = it.next().value;
// returns 3

var bool = it.next().done;
// returns true

The returned iterator protocol-compliant object has the following properties:

  • next: function which returns an iterator protocol-compliant object containing the next iterated value (if one exists) assigned to a value property and a done property having a boolean value indicating whether the iterator is finished.
  • return: function which closes an iterator and returns a single (optional) argument in an iterator protocol-compliant object.


  • Value "uniqueness" is determined according to strict equality.
  • A returned iterator internally buffers unique values and, thus, has O(N) memory requirements.
  • If an environment supports Symbol.iterator and a provided iterator is iterable, the returned iterator is iterable.


var discreteUniform = require( '@stdlib/random-iter-discrete-uniform' );
var iterUnique = require( '@stdlib/iter-unique' );

// Create a seeded iterator which can generate 1000 pseudorandom numbers:
var rand = discreteUniform( 1, 10, {
    'seed': 1234,
    'iter': 1000

// Create an iterator which returns unique values:
var it = iterUnique( rand );

// Perform manual iteration...
var v;
while ( true ) {
    v = it.next();
    if ( v.done ) {
    console.log( v.value );


This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.






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