inArray()?jQuery.inArray(value, array[, fromIndex]) (alias $.inArray) searches an array for a value with strict equality (since jQuery 1.2). It returns the index, or -1 if the value is missing.
$.inArray(value, array) → index | -1
$.inArray(value, array, fromIndex)
arr = [4, "Pete", 8, "John"]
$.inArray("John", arr) → 3
$.inArray(4, arr) → 0
$.inArray("Karl", arr) → -1
$.inArray("Pete", arr, 2) → -1| Need | Use |
|---|---|
| Find index | $.inArray(val, arr) |
| Is value present? | $.inArray(val, arr) !== -1 |
| Native index | arr.indexOf(val) |
| Native boolean | arr.includes(val) |
inArray()Pass the value, the array, and optionally where to start.
$.inArray(value, array).-1, the value was not found.fromIndex as the third argument.| Piece | Required? | Role |
|---|---|---|
value | Yes | Value to search for (strict ===) |
array | Yes | Array (or array-like) to search |
fromIndex | No | Start index (default 0) |
| Return | — | Index number, or -1 |
function inArray(value, array, fromIndex):
start = fromIndex or 0
for i from start to array.length - 1:
if array[i] === value: // strict equality
return i
return -1
// Membership check (safe):
found = inArray(value, array) !== -1Keep these facts handy while searching arrays with jQuery.
Search [4, "Pete", 8, "John"] with the official demo cases.
Short, copy-ready snippets. Open DevTools Console, or use Try It Yourself for a live editor.
Official pattern: search strings and numbers.
var arr = [4, "Pete", 8, "John"];
console.log($.inArray("John", arr)); // 3
console.log($.inArray(4, arr)); // 0"John" sits at index 3.4 is at index 0.0 means found at the start — not “missing”.Use !== -1 to ask “is it in the array?”
var arr = [4, "Pete", 8, "John"];
var idx = $.inArray("Karl", arr);
console.log(idx); // -1
console.log(idx !== -1); // false"Karl" is not in the list.$.inArray returns -1.idx !== -1 is the safe boolean test.fromIndexSkip earlier slots when you only care about the rest of the array.
var arr = [4, "Pete", 8, "John"];
console.log($.inArray("Pete", arr)); // 1
console.log($.inArray("Pete", arr, 2)); // -10, "Pete" is at 1.0 and 1."Pete" is already behind the start point.-1 even though the value exists earlier.Numbers and numeric strings are not the same.
// Official-style strict check
console.log($.inArray(5 + 5, ["8", "9", "10", 10 + ""]));
// → -1 (looking for number 10 in an array of strings)
console.log($.inArray("10", ["8", "9", "10"])); // 25 + 5 is the number 10.10 + "" becomes the string "10".10 === "10" is false, so the first search fails."10" finds index 2.Check these before using indexes in real code.
0 == false in loose checks. Always write !== -1 (or > -1) for membership.
4 and "4" are different. Normalize types before you search if your data is mixed.
A value can exist in the array and still return -1 if it only appears before fromIndex.
jQuery.inArray() is a data utility available since jQuery 1.2+ in all browsers that load jQuery. It does not need a special DOM API — only jQuery.
Works wherever jQuery runs in the browser. For modern pure-array code, Array.prototype.indexOf and includes are the native alternatives.
Bottom line: Use $.inArray(val, arr) in jQuery apps. Use arr.indexOf(val) or arr.includes(val) for native arrays.
| Approach | Cost | Best for |
|---|---|---|
$.inArray(val, arr) | O(n) | Small/medium lists |
arr.indexOf(val) | O(n) | Native arrays |
Set.has(val) | O(1) avg | Many membership checks |
Linear scan is fine for typical UI arrays. If you check membership thousands of times on the same list, build a Set once instead of repeating inArray.
$.inArray(val, arr) → index or -1.!== -1.===).One line: use $.inArray for a strict index lookup — treat -1 as missing, and never treat 0 as false.
Remove duplicate DOM nodes and sort them into document order.
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