timeout-queue

timeout-queue

Add items to the end of a queue. If the item is not pulled off the queue before time expires then the item will call it's callback function and be pulled off the queue immediately.

Installation

npm install timeout-queue

Usage

const timeoutQueue = require('timeout-queue');
const start = Date.now();

// items added to the queue set to persist for 500 ms before calling
// the expired function and removing the item from the queue
const queue = timeoutQueue(500, expired);

// add two items to the queue, both will expire in 500 ms
queue.push('Bob');
queue.push('Jan');

// output the queue length
console.log(queue.length);                      // 2

setTimeout(function() {
    const value = queue.next();
    console.log(time() + 'Got ' + value);       // "at 200 ms: Got Bob"
}, 200);

function expired(value) {
    console.log(time() + 'Expired ' + value);   // "at 500 ms: Expired Jan"
}

function time() {
    return 'at ' + (Date.now() - start) + ' ms: ';
}

API

timeoutQueue ( [ defaultTimeToLive ] [, timeoutCallback ] )

Get an instance of a timeout queue. Values added to the queue will last for the number of milliseconds specified in the defaultTimeToLive parameter. If they are not pulled off the queue before the value expires then the timeoutCallback function will be called with the value that was added to (and expired from) the queue.

Parameters

• defaultTimeToLive - The optional default number of milliseconds that a value will live on the queue before expiring. If set to a negative number then the default time to live will be to not expire. Defaults to -1.
• timeoutCallback - The optional callback function to call if the value added to the queue is not removed before the timeToLive expires.

Returns object with the next, push, and length,

Example

const timeoutQueue = require('timeout-queue');
const queue = timeoutQueue(500, function(value) {
    console.log('Expired ' + value);
});

#length

Get the length of the queue.

Returns a number.

Example

const timeoutQueue = require('timeout-queue');
const queue = timeoutQueue(500);

queue.push('Bob');

console.log(queue.length);         // 1

#next ( )

Get the next item off of the queue.

Returns the value of the item pulled off the queue.

Example

const timeoutQueue = require('timeout-queue');
const queue = timeoutQueue(500);

queue.push('Bob');

const value = queue.next();
console.log(value);         // "Bob"

#push ( value [, timeToLive ] [, callback ] )

Add a value to a timeout queue.

Parameters

• value - The value to add to the queue.
• timeToLive - An optional number specifying the number of seconds the value should remain on the queue. If omitted then the default time to live will be used.
• callback - An optional callback to call when the value is removed from the queue (either by expiring or not). The callback is passed two parameters: 1) the value, 2) a boolean specifying if it was removed because it expired.

Returns the value passed in.

Example 1: Value Only

const timeoutQueue = require('timeout-queue');
const queue = timeoutQueue(500, function(value) {
    console.log('Expired ' + value);
});

queue.push('Bob');

Example 2: Value Plus Custom Expiration

const timeoutQueue = require('timeout-queue');
const queue = timeoutQueue(500, function(value) {
    console.log('Expired ' + value);
});

queue.push('Bob', 700);

Example 3: Value Plus Extra Callback

const timeoutQueue = require('timeout-queue');
const queue = timeoutQueue(500, function(value) {
    console.log('Expired ' + value);
});

queue.push('Bob', removed);

function removed(value, expired) {
    console.log('Value removed: ' + value + ', Expired: ' + expired);
}

Example 4: All Arguments

const timeoutQueue = require('timeout-queue');
const queue = timeoutQueue(500, function(value) {
    console.log('Expired ' + value);
});

queue.push('Bob', 700, removed);

function removed(value, expired) {
    console.log('Value removed: ' + value + ', Expired: ' + expired);
}