# promise-map-series

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Call an iterator function for each element of an array in series, ensuring
that no iterator is called before the promise returned by the previous
iterator is fulfilled, in effect preventing parallel execution. Like
[async.mapSeries](https://github.com/caolan/async#mapseriesarr-iterator-callback),
but for promises.

## Installation

```bash
npm install --save promise-map-series
```

## Usage

```js
var mapSeries = require('promise-map-series')

mapSeries(array, iterator[, thisArg]).then(function (newArray) {
  ...
})
```

* **`array`**: An array of values (should not be promises).

* **`iterator`**: Function that returns a promise or a value for the new
  array. The `iterator` will be called once for each element. If `iterator`
  returns a promise, then `iterator` will only be called for the next element
  once that promise is fulfilled. If the promise is rejected or `iterator`
  throws an error, iteration will stop immediately and `mapSeries` returns a
  rejected promise. The `iterator` function receives three arguments:

    * **`item`**: The current item in the array.

    * **`index`**: The current index in the array.

    * **`array`**: The original `array` argument.

* **`thisArg`** (optional): Value to use as `this` when executing `iterator`.