Queue

Queue

new Queue(task, concurrency)

Run queued items through an asynchronous task.

Once finishing the task an optional callback is called. While pushing to the queue, you may define a priority for execution. Lower values means faster execution.

Parameters:
Name Type Description
task function

iterator function of type function (item: any, cb: Function, index: Number)
concurrency Number

max. number of tasks running in parallel
Source:
Examples

Default usage

var arr = []
var q = new Queue((item, cb) => {
  arr.push(item)
  cb(null, item)
})
// push item "one" at end of queue
q.push('one', (err, res) => {
  console.log(res + ' finished')
})
// add item "two" at start of queue
q.unshift('two', () => {
  console.log('two finished')
})
// called when all items in queue where processed
q.drain(() => {
  console.log(arr)
  //> arr = ['one', 'two']
})

Using priorities

let arr = []

let q = new Queue(function (item, cb) {
  arr.push(item)
  cb()
}, 2)

q.concat([100, 101, 102], 3) // priority = 3 - last (but 2 items already processed)
q.concat([0, 1, 2], 1)       // priority = 1 - first
q.concat([10, 11, 12], 2)    // priority = 2 - second

q.drain(() => {
  //> arr = [ 100, 101, 0, 1, 2, 10, 11, 12, 102 ])
})

Members

idle

Check if queue is idle - means no items in queue and no workers running

Source:

length

Number of items waiting in the queue to get processed

Source:

paused

Check if queue is paused

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Methods

concat(items, callbackopt, priorityopt) → {this}

concat items onto queue - fills the queue first with items before starting processing

Parameters:
Name Type Attributes Description
items Array.<Any>
callback function <optional>

optional callback if single item was processed
priority Number <optional>

priority 0 ... Infinity of the item to process. Smaller values, faster processing
Source:
Returns:

for chaining

Type
this

drain(callbackopt) → {this}

Parameters:
Name Type Attributes Description
callback function <optional>

optional callback called if all queue items got processed
Source:
Returns:

for chaining

Type
this

pause() → {this}

Pause processing

Source:
Returns:

for chaining

Type
this

push(item, callbackopt, priorityopt) → {this}

push item onto queue

Parameters:
Name Type Attributes Description
item Any
callback function <optional>

optional callback if item was processed
priority Number <optional>

priority 0 ... Infinity of the item to process. Smaller values, faster processing
Source:
Returns:

for chaining

Type
this

reset() → {this}

Reset the queue by removing all pending items from the queue

Source:
Returns:

for chaining

Type
this

resume() → {this}

Resume processing

Source:
Returns:

for chaining

Type
this

running() → {Number}

Number of items being processed

Source:
Returns:

number of items processed

Type
Number

unshift(item, callbackopt) → {this}

put item at the very beginnning of the queue

Parameters:
Name Type Attributes Description
item Any
callback function <optional>

optional callback if item was processed
Source:
Returns:

for chaining

Type
this