progress-stream

2018-09-15 admin

progress-stream是什么

什么是progress-stream,Read the progress of a stream

progress-stream使用教程帮助文档

progress-stream

Read the progress of a stream. Supports speed and eta.

Gets the length of the stream automatically if you’re using the request or http module. You can also pass the length on initiation. Progress-stream will also check to see if the stream already has a length property.

npm install progress-stream

Usage

This example copies a large file, and prints out the percentage, speed and remaining every 100ms.

var progress = require('progress-stream');
var fs = require('fs');

var stat = fs.statSync(filename);
var str = progress({
	length: stat.size,
	time: 100 /* ms */
});

str.on('progress', function(progress) {
	console.log(progress);

	/*
	{
		percentage: 9.05,
		transferred: 949624,
		length: 10485760,
		remaining: 9536136,
		eta: 42,
		runtime: 3,
		delta: 295396,
		speed: 949624
	}
	*/
});

fs.createReadStream(filename)
	.pipe(str)
	.pipe(fs.createWriteStream(output));

Methods

progress([options], [onprogress])

You can instantiate in two ways:

var str = progress({time:100});
str.on('progress', function(progress) { ... });

or inline the progress listener

var str = progress({time:100}, function(progress) { ... });

Properties

.progress()

You can get the progress from the progress function.

var str = progress({time:100});

console.log(str.progress());

/*
{
	percentage: 9.05,
	transferred: 949624,
	length: 10485760,
	remaining: 9536136,
	eta: 10,
	runtime: 0,
	delta: 295396,
	speed: 949624
}
*/

Events

on(‘progress’, function(progress) { … })

var str = progress({time:100});
str.on('progress', function(progress) { ... });

Options

time(integer)

Sets how often progress events are emitted in ms. If omitted then the default is to do so every time a chunk is received.

speed(integer)

Sets how long the speedometer needs to calculate the speed. Defaults to 5 sec.

length(integer)

If you already know the length of the stream, then you can set it. Defaults to 0.

drain(boolean)

In case you don’t want to include a readstream after progress-stream, set to true to drain automatically. Defaults to false.

transferred(integer)

If you want to set the size of previously downloaded data. Useful for a resumed download.

Examples

Using the request module

This example uses request to download a 100 MB file, and writes out the percentage every second.

You can also find an example in test/request.js.

var progress = require('progress-stream');
var req = require('request');
var fs = require('fs');

var str = progress({
	time: 1000
});

str.on('progress', function(progress) {
	console.log(Math.round(progress.percentage)+'%');
});

req('http://cachefly.cachefly.net/100mb.test', { headers: { 'user-agent': 'test' }})
	.pipe(str)
	.pipe(fs.createWriteStream('test.data'));

Using the http module

In test/http.js it’s shown how to do it with the http module.

Methods

setLength(newLength)

Sometimes, you don’t know how big a stream is right away (e.g. multipart file uploads). You might find out after a few chunks have already passed through the stream, seconds or even minutes later. In this case, you can use the setLength method to recalculate the relevant tracked progress data.

var str = progress({});
someFickleStreamInstance.pipe(str).pipe(fs.createWriteStream('test.data'));

someFickleStreamInstance.on('conviction', function nowIKnowMyLength (actualLength) {
  str.setLength(actualLength);
});

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