1.2.0 • Published 1 year ago
@vweevers/peek-stream v1.2.0
peek-stream
Transform stream that lets you peek the first line before deciding how to parse it. Fork of mafintosh/peek-stream
(1.1.3) to add #8.
npm install @vweevers/peek-stream
Usage
var peek = require('@vweevers/peek-stream')
var ldjson = require('ldjson-stream')
var csv = require('csv-parser')
var isCSV = function(data) {
return data.toString().indexOf(',') > -1
}
var isJSON = function(data) {
try {
JSON.parse(data)
return true
} catch (err) {
return false
}
}
// call parser to create a new parser
var parser = function() {
return peek(function(data, swap) {
// maybe it is JSON?
if (isJSON(data)) return swap(null, ldjson())
// maybe it is CSV?
if (isCSV(data)) return swap(null, csv())
// we do not know - bail
swap(new Error('No parser available'))
})
}
The above parser will be able to parse both line delimited JSON and CSV
var parse = parser()
parse.write('{"hello":"world"}\n{"hello":"another"}\n')
parse.on('data', function(data) {
console.log(data) // prints {hello:'world'} and {hello:'another'}
})
Or
var parse = parser()
parse.write('test,header\nvalue-1,value-2\n')
parse.on('data', function(data) {
console.log(data) // prints {test:'value-1', header:'value-2'}
})
Per default data
is the first line (or the first 65535
bytes if no newline is found).
To change the max buffer pass an options map to the constructor
var parse = peek({
maxBuffer: 10000
}, function(data, swap) {
...
})
If you want to emit an error if no newline is found set strict: true
as well.
Normally data
is written to the swapped stream as-is. To override data
, pass a third argument to swap
:
var parse = peek(function(data, swap) {
// Strip utf-8 byte order mark
if (data.byteLength >= 3 && data[0] === 0xef && data[1] === 0xbb && data[2] === 0xbf) {
data = data.subarray(3)
}
if (isCSV(data)) {
// The csv stream will not receive the BOM
swap(null, csv(), data)
return
}
swap(new Error('No parser available'))
})
License
MIT
1.2.0
1 year ago