LPOP

Remove and return the first element(s) of a list

Overview

Removes and returns the first element of the list stored at key. When a count is provided, removes and returns up to count elements.

Method Signature

lpop<TData = string>(key: string): Promise<TData | null>
lpop<TData = string[]>(key: string, count: number): Promise<TData | null>

Parameters

key · string · required

The key of the list.

count · number

The number of elements to pop. When specified, returns an array of elements instead of a single element.

Return Value

element · TData | null

When called without count: The first element of the list, or null if the list is empty or does not exist.

When called with count: An array of popped elements, or null if the list is empty or does not exist.

Examples

Basic Usage

import { Redis } from '@upstash/redis';

const redis = new Redis({
  url: process.env.UPSTASH_REDIS_REST_URL,
  token: process.env.UPSTASH_REDIS_REST_TOKEN,
});

// Set up a list
await redis.lpush('mylist', 'world', 'hello');
// List is: ['hello', 'world']

// Pop the first element
const element = await redis.lpop('mylist');
console.log(element); // 'hello'

// Pop from empty list
const empty = await redis.lpop('nonexistent');
console.log(empty); // null

Pop Multiple Elements

// Set up a list
await redis.rpush('queue', 'job-1', 'job-2', 'job-3', 'job-4');

// Pop multiple elements
const jobs = await redis.lpop<string[]>('queue', 2);
console.log(jobs); // ['job-1', 'job-2']

Working with Objects

interface Task {
  id: string;
  title: string;
  priority: number;
}

// Add tasks
await redis.lpush<Task>('tasks', {
  id: '123',
  title: 'Complete documentation',
  priority: 1,
});

// Pop the task
const task = await redis.lpop<Task>('tasks');
console.log(task?.title); // 'Complete documentation'

Queue Processing

// Process items from the head of a queue
while (true) {
  const item = await redis.lpop('queue:processing');
  
  if (!item) {
    break; // Queue is empty
  }
  
  // Process the item
  await processItem(item);
}

Batch Processing

// Process multiple items at once
const batchSize = 10;
const batch = await redis.lpop<string[]>('queue:batch', batchSize);

if (batch) {
  await Promise.all(batch.map(item => processItem(item)));
}

See Also

• RPOP - Remove and return the last element of a list
• LPUSH - Insert elements at the head of a list
• LRANGE - Get a range of elements from a list
• LLEN - Get the length of a list