jQuery jQuery.inArray() Method

What You’ll Learn

The jQuery.inArray() utility searches an array for a value and returns its index — or -1 when the value is missing. This tutorial covers syntax, the optional fromIndex parameter, five worked examples, comparisons with indexOf() and includes(), and practical membership-check patterns.

Introduction

Searching a list for a specific value is one of the most common programming tasks. Is this ID in the allowed list? Which slot holds the user’s selection? jQuery provides jQuery.inArray() (also written $.inArray()) as a static utility that answers: where is this value?

Unlike jQuery.grep(), which filters with a custom function, inArray looks for one exact value using strict equality. The return value is a number — the index when found, or -1 when not found — matching the familiar behavior of Array.prototype.indexOf().

Understanding the jQuery.inArray() Method

jQuery.inArray(value, array [, fromIndex]) walks the array from left to right (starting at fromIndex when provided) and compares each element to value with ===. The first matching index is returned; if no match exists, the method returns -1.

The input collection can be a true array or any array-like object with length and indexed values — the same kinds of collections $.grep() and $.merge() accept.

📝 Syntax

General form of jQuery.inArray:

jQuery.inArray( value, array [, fromIndex ] )
// or
$.inArray( value, array [, fromIndex ] )

Parameters

• value — the item to search for. Compared with strict equality (===) against each element.
• array — an array or array-like object to search through.
• fromIndex (optional) — index at which to begin searching. Defaults to 0. A negative value counts from the end of the array.

Return value

• The zero-based index of the first matching element.
• -1 if value is not found.

Minimal workflow

var names = ["Ann", "Bob", "Carl"];
var idx = $.inArray("Bob", names);

console.log(idx); // 1

Examples Gallery

Each example uses $.inArray(). Open DevTools or use the Try-it links to run them interactively.

var arr = [4, "Pete", 8, "John"];

console.log($.inArray("John", arr)); // 3
console.log($.inArray(4, arr));      // 0
console.log($.inArray(8, arr));      // 2

3
0
2

var arr = [4, "Pete", 8, "John"];
var idx = $.inArray("David", arr);

console.log(idx);                    // -1
console.log(idx === -1);             // true — not in the array

-1
true

var arr = [4, "Pete", 8, "John"];

console.log($.inArray(4, arr));    // 0  — number 4 at index 0
console.log($.inArray("4", arr));  // -1 — string "4" is not strictly equal

0
-1

var arr = [4, "Pete", 8, "John"];

console.log($.inArray("Pete", arr));     // 1 — found at index 1
console.log($.inArray("Pete", arr, 2));   // -1 — search starts at index 2, skips index 1

1
-1

var allowedRoles = ["admin", "editor", "viewer"];
var userRole = "editor";

if ($.inArray(userRole, allowedRoles) !== -1) {
  console.log("Access granted for: " + userRole);
} else {
  console.log("Access denied");
}
// Access granted for: editor

Access granted for: editor

🚀 Common Use Cases

• Whitelist validation — confirm a role, status, or category string is allowed.
• Tab or menu state — find which index matches the active item ID.
• Duplicate detection — check whether a value already exists before pushing to an array.
• Partial search — use fromIndex to locate a second occurrence.
• Plugin configuration — test whether an option appears in a supported-options array.
• Legacy jQuery codebases — consistent search before includes() was widely available.

📝 Notes

• Available since jQuery 1.2 — one of the core array utilities.
• Uses strict equality (===) — no type coercion.
• Never use the result as a bare boolean — index 0 is falsy.
• Returns only the first match; duplicates after that are ignored unless you use fromIndex.
• Works on array-like objects, not plain key/value objects.
• For complex matching rules (partial strings, ranges), use $.grep() instead.

💡 Best Practices