collection.indexOf(item) - Get Index of Item

Quick Start (30 seconds)

const fruits = createCollection(['apple', 'banana', 'orange', 'banana']);

// Find index
const index = fruits.indexOf('banana');
console.log(index);  // 1

// Not found returns -1
const notFound = fruits.indexOf('grape');
console.log(notFound);  // -1

// Find index to remove
const idx = fruits.indexOf('orange');
if (idx !== -1) {
  fruits.items.splice(idx, 1);
}

// Check if item exists
if (fruits.indexOf('apple') !== -1) {
  console.log('We have apples!');
} ✨

What just happened? You found the position of an item in the collection!

What is collection.indexOf(item)?

indexOf(item) returns the first index where the item is found, or -1 if not found.

Simply put: it tells you the position of an item in the collection.

Think of it as finding a page number in a book - you get the location or -1 if it's not there.

Syntax

collection.indexOf(item)

Parameters:

• item (any) - The item to search for (uses strict equality ===)

Returns:

• Index (number) - Position of first match (0-based)
• -1 if not found

Why Does This Exist?

The Problem:

// Must access .items
const index = collection.items.indexOf('apple');

The Solution:

// Direct collection API
const index = collection.indexOf('apple');

Basic Usage

const numbers = createCollection([10, 20, 30, 40, 30]);

numbers.indexOf(30);  // 2 (first occurrence)
numbers.indexOf(99);  // -1 (not found)

Real-World Examples

Example 1: Remove by Value

const tags = createCollection(['js', 'react', 'vue']);

function removeTag(tag) {
  const idx = tags.indexOf(tag);
  if (idx !== -1) {
    tags.items.splice(idx, 1);
  }
}

removeTag('react');

Example 2: Check Position

const queue = createCollection(['alice', 'bob', 'charlie']);

function getPosition(name) {
  const idx = queue.indexOf(name);
  return idx !== -1 ? `Position: ${idx + 1}` : 'Not in queue';
}

console.log(getPosition('bob'));  // "Position: 2"

Important Notes

1. Returns First Index Only

const items = createCollection(['a', 'b', 'a', 'c']);
items.indexOf('a');  // 0 (first occurrence)

2. Uses Strict Equality

const nums = createCollection([1, 2, 3]);
nums.indexOf('2');  // -1 (string !== number)
nums.indexOf(2);    // 1 ✓

3. Returns -1 if Not Found

if (collection.indexOf(item) !== -1) {
  console.log('Found!');
}

When to Use

Use indexOf() For: ✅ Get item position
✅ Check if exists
✅ Remove by value

Don't Use For: ❌ Complex searches - Use find()
❌ Get item - Use at() or find()

Summary

What is indexOf(item)?
Returns the index of the first matching item or -1.

Remember: Returns -1 if not found, uses strict equality! 🎉