Modern JavaScript (ES2023)

Array findLast/findLastIndex

Find elements from the end of arrays - search backwards!

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What are findLast & findLastIndex?

findLast() andfindLastIndex() search arrays from the end backwards! Just like find() andfindIndex(), but in reverse. Perfect for finding the last matching element!

Mirror of find/findIndex!

Same API as find() andfindIndex(), just searches from the end!

Example 1: Finding from the End

Use findLast() and findLastIndex() to search backwards

javascript

code

DarkEditable

const numbers = [5, 12, 8, 130, 44, 12, 7];

// find() - searches from start
const firstLarge = numbers.find(n => n > 10);
console.log(firstLarge);  // 12 (first match)

// findLast() - searches from end
const lastLarge = numbers.findLast(n => n > 10);
console.log(lastLarge);  // 12 (last match, at index 5)

// findIndex() - index of first match
const firstIndex = numbers.findIndex(n => n > 10);
console.log(firstIndex);  // 1

// findLastIndex() - index of last match
const lastIndex = numbers.findLastIndex(n => n > 10);
console.log(lastIndex);  // 5

// Finding objects
const users = [
  { id: 1, name: 'Alice', active: true },
  { id: 2, name: 'Bob', active: false },
  { id: 3, name: 'Charlie', active: true },
  { id: 4, name: 'Diana', active: true }
];

// Last active user
const lastActive = users.findLast(user => user.active);
console.log(lastActive);
// { id: 4, name: 'Diana', active: true }

// Index of last active user
const lastActiveIndex = users.findLastIndex(user => user.active);
console.log(lastActiveIndex);  // 3

// Not found returns undefined/-1
const arr = [1, 2, 3];
console.log(arr.findLast(n => n > 10));       // undefined
console.log(arr.findLastIndex(n => n > 10));  // -1

Console Output

Click "Run Code" to see output here...

Example 2: Real-World Use Cases

Practical scenarios for searching from the end

javascript

code

DarkEditable

// 1. Get most recent matching item
const transactions = [
  { id: 1, type: 'deposit', amount: 100, date: '2024-01-01' },
  { id: 2, type: 'withdrawal', amount: 50, date: '2024-01-02' },
  { id: 3, type: 'deposit', amount: 200, date: '2024-01-03' },
  { id: 4, type: 'withdrawal', amount: 75, date: '2024-01-04' }
];

const lastDeposit = transactions.findLast(t => t.type === 'deposit');
console.log(lastDeposit);
// { id: 3, type: 'deposit', amount: 200, date: '2024-01-03' }

// 2. Find last error in logs
const logs = [
  { level: 'info', message: 'Started' },
  { level: 'error', message: 'Connection failed' },
  { level: 'info', message: 'Retrying' },
  { level: 'error', message: 'Timeout' }
];

const lastError = logs.findLast(log => log.level === 'error');
console.log(lastError.message);  // "Timeout"

// 3. Find last occurrence in sorted data
const scores = [45, 67, 78, 82, 82, 90, 95];

// Last score below 90
const lastBelow90 = scores.findLast(score => score < 90);
console.log(lastBelow90);  // 82

// 4. Get most recent version
const versions = [
  { version: '1.0.0', stable: true },
  { version: '1.1.0', stable: false },
  { version: '1.2.0', stable: true },
  { version: '2.0.0', stable: false }
];

const latestStable = versions.findLast(v => v.stable);
console.log(latestStable.version);  // "1.2.0"

// 5. Remove last matching item (using findLastIndex)
function removeLastMatch(arr, predicate) {
  const index = arr.findLastIndex(predicate);
  if (index !== -1) {
    arr.splice(index, 1);
  }
  return arr;
}

const items = ['a', 'b', 'c', 'b', 'd'];
removeLastMatch(items, item => item === 'b');
console.log(items);  // ['a', 'b', 'c', 'd']

Console Output

Click "Run Code" to see output here...

Comparison Table

Method	Direction	Returns
`find()`	Start → End	First match or undefined
`findLast()`	End → Start	Last match or undefined
`findIndex()`	Start → End	First index or -1
`findLastIndex()`	End → Start	Last index or -1

Key Takeaways

◀️

Search Backwards

Starts from end and works towards beginning

🔍

Same API

Works like find/findIndex, just reversed

📅

Most Recent

Perfect for finding latest matching items

💡

ES2023

Latest array search methods

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Error.cause

Chaining errors with cause property for better debugging (ES2022).

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Immutable Array Methods

toSorted(), toReversed(), toSpliced(), with() for immutable operations (ES2023).

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Output

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Modern JavaScript (ES2023)

Array findLast/findLastIndex

Find elements from the end of arrays - search backwards!

Find videos you like?

Save to resource drawer for future reference!

What are findLast & findLastIndex?

findLast() andfindLastIndex() search arrays from the end backwards! Just like find() andfindIndex(), but in reverse. Perfect for finding the last matching element!

Mirror of find/findIndex!

Same API as find() andfindIndex(), just searches from the end!

Example 1: Finding from the End

Use findLast() and findLastIndex() to search backwards

javascript

code

DarkEditable

const numbers = [5, 12, 8, 130, 44, 12, 7];

// find() - searches from start
const firstLarge = numbers.find(n => n > 10);
console.log(firstLarge);  // 12 (first match)

// findLast() - searches from end
const lastLarge = numbers.findLast(n => n > 10);
console.log(lastLarge);  // 12 (last match, at index 5)

// findIndex() - index of first match
const firstIndex = numbers.findIndex(n => n > 10);
console.log(firstIndex);  // 1

// findLastIndex() - index of last match
const lastIndex = numbers.findLastIndex(n => n > 10);
console.log(lastIndex);  // 5

// Last active user
const lastActive = users.findLast(user => user.active);
console.log(lastActive);
// { id: 4, name: 'Diana', active: true }

// Index of last active user
const lastActiveIndex = users.findLastIndex(user => user.active);
console.log(lastActiveIndex);  // 3

// Not found returns undefined/-1
const arr = [1, 2, 3];
console.log(arr.findLast(n => n > 10));       // undefined
console.log(arr.findLastIndex(n => n > 10));  // -1

Console Output

Click "Run Code" to see output here...

Example 2: Real-World Use Cases

Practical scenarios for searching from the end

javascript

code

DarkEditable

const lastDeposit = transactions.findLast(t => t.type === 'deposit');
console.log(lastDeposit);
// { id: 3, type: 'deposit', amount: 200, date: '2024-01-03' }

const lastError = logs.findLast(log => log.level === 'error');
console.log(lastError.message);  // "Timeout"

// 3. Find last occurrence in sorted data
const scores = [45, 67, 78, 82, 82, 90, 95];

// Last score below 90
const lastBelow90 = scores.findLast(score => score < 90);
console.log(lastBelow90);  // 82

const latestStable = versions.findLast(v => v.stable);
console.log(latestStable.version);  // "1.2.0"

const items = ['a', 'b', 'c', 'b', 'd'];
removeLastMatch(items, item => item === 'b');
console.log(items);  // ['a', 'b', 'c', 'd']

Console Output

Click "Run Code" to see output here...

Comparison Table

Method	Direction	Returns
`find()`	Start → End	First match or undefined
`findLast()`	End → Start	Last match or undefined
`findIndex()`	Start → End	First index or -1
`findLastIndex()`	End → Start	Last index or -1

Key Takeaways

◀️

Search Backwards

Starts from end and works towards beginning

🔍

Same API

Works like find/findIndex, just reversed

📅

Most Recent

Perfect for finding latest matching items

💡

ES2023

Latest array search methods

Coder Pod - Learn Programming Online | AI Coding Tutor & Interview Practice

Error.cause

Immutable Array Methods

JavaScript Code Editor

Building Your Learning Module...

Array findLast/findLastIndex

What are findLast & findLastIndex?

Mirror of find/findIndex!

Example 1: Finding from the End

Example 2: Real-World Use Cases

Key Takeaways

Search Backwards

Same API

Most Recent

ES2023

Error.cause

Immutable Array Methods

JavaScript Code Editor

Array findLast/findLastIndex

What are findLast & findLastIndex?

Mirror of find/findIndex!

Example 1: Finding from the End

Example 2: Real-World Use Cases

Key Takeaways

Search Backwards

Same API

Most Recent

ES2023