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Iterate through multiple files or streams at the same time line by line without loading into memory.

# Install
```npm install iterate-multiple-files```

# Code Example

## iterate

```javascript
import imf from 'iterate-multiple-files';

let runningSum = 0;

//The function will receive an array of lines in the same order as the input file paths
function operation(lines){
  // The return statement will ensure that the value gets appended to the final
  // array returned either in the promise or callback. If you do not return anything
  // then nothing will be saved to the array - this is good if dealing with large 
  // files and running out of memory.

  // Do any operation in here
  const lineSum = parseInt(lines[0]) + parseInt(lines[1]);
  runningSum += lineSum;
  return lineSum
}

//Using a promise:
//You can pass in all files, all Readable streams or a combination of both in the same array
imf.iterate(['path-to-file1','path-to-file2', fs.createReadStream('path-to-file3')],operation)
  .then(function(result){
    //Do something with the result
    //Result is an array of each line's sum
  })
  .catch(function(err){
    //Handle the error
  });
```
### Using a callback
```javascript
//Using a callback:
//You can pass in all files, all Readable streams or a combination of both in the same array
imf.iterate(['path-to-file1','path-to-file2',fs.createReadStream('path-to-file3')],operation, function(err, result){
  if(err){
    //Handle the error
  }
  //Do something with result
});
```

## Iterator functionality
Will come in a TBD version

## Generator functionality
Will come in a TBD version

# Motivation
Perform operations line by line on files too large to load in memory.

# Contributors
If you are interested in contributing please contact oskari.rautiainen@gmail.com

# License

[MIT](https://vjpr.mit-license.org)