lib/modifiers/map.js
function map(transform) {
  var cb = makeAsync(transform, 2);

  return through.obj(function (value, enc, next) {
    cb(value, next);
  });
}
function map(transform) {
  var cb = makeAsync(transform, 2);

  return through.obj(function (value, enc, next) {
    cb(value, next);
  });
}
function map ( transform ) { var cb = makeAsync ( transform , 2 ) ; return through . obj ( function ( value , enc , next ) { cb ( value , next ) ; } ) ; }
Creates a new stream with the results of calling the provided function on
every item in the stream. Similar to Array.map... but on a stream.

@static
@since    1.0.0
@category Modifiers

@param    {Function} transform - Function that returns a new element on the
stream. Takes one argument, the value of the
item at this position in the stream.
@returns  {Stream.Transform}   - A transform stream with the modified values.

@example

// For a simple find/replace, you could do something like the following. Assuming
// "example.txt" is a file with the text "the text has periods. because, english.",
// you could replace each period with a comma like so:
fs.createReadStream('example.txt')
.pipe(nodeStream.map(value => value.toString().replace('.', ',')));

// The resulting stream will have the value "the text has periods, because, english,".

@example

// It is also possible to transform a stream asynchronously for more complex actions.
// Note: The signature of the function that you pass as the callback is important. It
// MUST have *two* parameters.

// Assuming "filenames.txt" is a newline-separated list of file names, you could
// create a new stream with their contents by doing something like the following:
fs.createReadStream('filenames.txt')
.pipe(nodeStream.split()) // split on new lines
.pipe(nodeStream.map((value, next) => {
fs.readFile(value, next);
}));

// The resulting stream will contain the text of each file. Note: If `next` is called
// with an error as the first argument, the stream will error. This is typical behavior
// for node callbacks.
Creates a new stream with the results of calling the provided function on every item in the stream . Similar to Array . map ... but on a stream .