jQuery jQuery.unique() Method

What You’ll Learn

The jQuery.unique() utility removes duplicate DOM node references from an array and sorts the remaining elements into document order. Deprecated since jQuery 3.0 (alias of uniqueSort), it remains essential for reading legacy tutorials. This page covers syntax, identity-based deduplication, five worked examples, migration to $.uniqueSort(), and when each name appears in the wild.

Introduction

When you combine DOM results from multiple jQuery selectors, the same element can appear more than once in your working array. jQuery provides jQuery.unique() (also written $.unique()) to clean that list: it strips duplicate node references and orders what remains according to where each element sits in the document.

This name dates back to early jQuery releases. In jQuery 3.0 it was renamed to jQuery.uniqueSort() to avoid confusion with other “unique” APIs, but $.unique() still works as a deprecated alias. You will see it in older blog posts, Stack Overflow answers, and plugins written for jQuery 1.x and 2.x.

Understanding the jQuery.unique() Method

jQuery.unique(array) accepts a native array (or array-like object) whose items are DOM elements. It modifies that array in place, removes entries that point to the same node object twice, and sorts survivors into document order. The return value is the same array reference, now shorter and ordered.

Duplicate detection is strict: only the exact same node counts as a duplicate. Two separate <div> elements with matching classes or ids remain distinct entries. This method does not deduplicate strings, numbers, or plain objects.

📝 Syntax

General form of jQuery.unique:

jQuery.unique( array )
// or
$.unique( array )

Parameters

• array — a native array or array-like object containing DOM elements. This collection is modified in place.

Return value

• Returns the same array reference, now deduplicated and sorted in document order.

Minimal workflow

var nodes = $("div").get();
nodes = nodes.concat($(".highlight").get());
nodes = $.unique(nodes);

Examples Gallery

Each example uses DOM elements and $.unique() — the legacy name you will encounter in older jQuery documentation. Open DevTools or use the Try-it links to run them interactively. Example 1 follows the official jQuery API demo pattern.

// unique() must take a native array
var divs = $("div").get();

// Add elements matched by .dup (they are divs too)
divs = divs.concat($(".dup").get());

console.log("Pre-unique:", divs.length);

divs = $.unique(divs);

console.log("Post-unique:", divs.length);

Pre-unique: 8
Post-unique: 6

var target = document.getElementById("panel");
var nodes = [target, target, target];

console.log("Before:", nodes.length);

$.unique(nodes);

console.log("After:", nodes.length);
console.log(nodes[0] === target); // true

Before: 3
After: 1
true

var items = $("li.item").get();

console.log("Before:", items.length);

$.unique(items);

console.log("After:", items.length);
// Still 3 — three distinct node objects in the DOM

Before: 3
After: 3

var nodes = [
  document.querySelector("#third"),
  document.querySelector("#first"),
  document.querySelector("#second")
];

$.unique(nodes);

console.log(
  nodes.map(function (el) { return el.id; }).join(" → ")
);
// "first → second → third"

first → second → third

var nodes = $("nav a").get();
$.merge(nodes, $(".footer-link").get());

console.log("Merged length:", nodes.length);

// Before (jQuery 1.x / 2.x style)
// $.unique(nodes);

// After (jQuery 3+ recommended)
$.uniqueSort(nodes);

console.log("Unique length:", nodes.length);

$(nodes).addClass("tracked");

Merged length: 5
Unique length: 4

🚀 Common Use Cases

• Reading legacy tutorials — recognize $.unique() in jQuery 1.x/2.x docs and older blog posts.
• Maintaining old plugins — understand dedupe logic before renaming to uniqueSort.
• Combined selectors — dedupe after merging results from multiple jQuery queries.
• Internal jQuery pipelines — jQuery called this internally before the 3.0 rename.
• Document-order guarantees — rely on sorted output before iterating for layout-sensitive work.
• Debugging overlap — inspect array length before/after when selectors unexpectedly double-count nodes.

📝 Notes

• jQuery.unique() has existed since early jQuery; deprecated in jQuery 3.0 in favor of jQuery.uniqueSort().
• Since jQuery 1.4, results are always sorted in document order.
• Only works on arrays of DOM elements — not strings, numbers, or generic objects.
• Modifies the input array in place; clone first if you need the original list preserved.
• Convert jQuery collections with .get() or .toArray() before calling.
• Chiefly an internal jQuery helper — most application code never calls it directly.

💡 Best Practices