Line Transform Stream

A transform stream class to conveniently modify streamable data line by line. Written in ES2015/ES6.

• Encodes input data chunk as string
• Splits input at newline characters and buffers incomplete lines
• Runs callback on each complete line
• Outputs processed lines

Usage

Pass your transform function to the constructor. This example reads lines from stdin, replaces whitespaces by underscores and writes back to stdout.

// import module
const LineTransformStream = require( 'line-transform-stream' )

// create new line transform stream
const filter = new LineTransformStream( ( line ) =>
{
    // replace every whitespace by an underscore
    return line.replace( /\s/g, '_' )
})

// say hello
process.stdout.write( "Type a phrase and hit Enter:\n" )

// connect stdin via transform stream to stdout
process.stdin.pipe( filter ).pipe( process.stdout )

Reference

new LineTransformStream( transformCallback, stringEncoding, newlineCharacter )

• transformCallback Function Callback to process a line of text. Called with a String as single argument, without the newline at the end. Must return a String or throw an Error. Any thrown Error is caught and emitted as stream error event.
• stringEncoding String Optional. Specifies a valid encoding option for Buffer.toString(). Defaults to "utf8".
• newlineCharacter String Optional. Specifies a string to split the input at. Defaults to "\n".