jQuery.merge()?jQuery.merge(first, second) (alias $.merge) appends items from second onto the end of first, preserves order, and returns the updated first array (since jQuery 1.0).
$.merge(first, second) → first (modified)
$.merge([0, 1, 2], [2, 3, 4])
→ [0, 1, 2, 2, 3, 4] // duplicates kept
// Clone:
$.merge([], oldArray)
// Merge without changing sources:
$.merge($.merge([], first), second)| Need | Use |
|---|---|
| Append into first (in place) | $.merge(first, second) |
| New array, both unchanged | first.concat(second) |
| Merge object keys | $.extend(a, b) |
jQuery.merge()Pass two array-like values; second is appended onto first.
first (the array that will grow) and second (source to append).$.merge(first, second).first).first unchanged, merge into a clone: $.merge($.merge([], first), second).| Piece | Required? | Role |
|---|---|---|
first | Yes | Target array-like — modified in place |
second | Yes | Items to append — left unaltered |
| Return | — | The merged first array |
function merge(first, second):
for each item in second:
append item to first
update first.length
return first
// Official clone shortcut:
newArray = merge([], oldArray)
// Official safe combine:
result = merge(merge([], first), second)Keep these facts handy while combining arrays.
| Topic | Detail |
|---|---|
| Syntax | jQuery.merge(first, second) |
| Since | jQuery 1.0 |
| Mutates? | Yes — first only |
| Order | Preserved; second appended |
| Duplicates | Kept (not unique) |
| Clone | $.merge([], arr) |
| Pre-1.4 | True arrays; else $.makeArray |
Run official-style $.merge demos: append, clone, or safe combine.
Short, copy-ready snippets. Open DevTools Console, or use Try It Yourself for a live editor.
Append the second array onto the first — duplicates stay.
var first = [0, 1, 2];
$.merge(first, [2, 3, 4]);
console.log(first); // [0, 1, 2, 2, 3, 4]first starts as [0, 1, 2].[2, 3, 4] are pushed onto the end.2 appears twice — merge does not unique.first itself is the result array.First-array items stay in front; second is appended in its own order.
var first = [3, 2, 1];
$.merge(first, [4, 3, 2]);
console.log(first); // [3, 2, 1, 4, 3, 2]3, 2, 1 stay at the start.4, 3, 2 follow in the same order.Official shortcut: merge into [] to shallow-copy.
var original = ["a", "b", "c"];
var copy = $.merge([], original);
console.log(copy); // ["a", "b", "c"]
console.log(copy === original); // false[].original are appended into that new array.copy === original is false.Nest two merges so both originals stay intact.
var first = ["a", "b", "c"];
var second = ["d", "e", "f"];
var combined = $.merge($.merge([], first), second);
console.log(combined); // ["a", "b", "c", "d", "e", "f"]
console.log(first); // ["a", "b", "c"]
console.log(second); // ["d", "e", "f"]$.merge([], first) clones first.second onto that clone.first nor second is mutated.first.concat(second) is often clearer for this case.Grow one results list as each page arrives.
var allRows = ["Row 1", "Row 2"];
$.merge(allRows, ["Row 3", "Row 4"]);
$.merge(allRows, ["Row 5"]);
console.log(allRows.join(" | "));
// "Row 1 | Row 2 | Row 3 | Row 4 | Row 5"allRows is the growing first array.Check these before merging arrays in real projects.
Always treat first as mutated. Clone first if callers still need the original list.
Merge is not unique. Use $.uniqueSort() only for DOM node arrays when you need document-order uniqueness.
Object key merges belong to $.extend(). $.merge appends indexed items.
Older jQuery required real arrays. Convert with $.makeArray() when supporting very old builds.
jQuery.merge() needs jQuery in the browser. It has been available since jQuery 1.0+ in all browsers your jQuery build supports. Array-like arguments are accepted in modern jQuery (1.4+).
Works in Chrome, Firefox, Safari, Edge, and other browsers with jQuery loaded. Append array-like collections into the first array in place.
Bottom line: Use $.merge(first, second) to append in place — clone with $.merge([], arr) when you need a copy.
| Approach | Cost | Best for |
|---|---|---|
$.merge(a, b) | O(|b|) | In-place append / accumulators |
a.concat(b) | O(|a|+|b|) | Immutable combine |
$.merge([], a) | O(|a|) | Shallow clone |
Prefer in-place merge when building one growing list. Prefer concat when immutability matters more than reuse of the first array.
$.merge(first, second) appends onto first.first changes; second is untouched.$.merge([], arr) or nest merges for a safe combine.One line: $.merge(first, second) appends second onto first in place — clone first when you need the original.
Convert NodeLists and jQuery collections into true JavaScript arrays.
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