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---
title: "async(type[, onUpdate])"
layout: default
section: api
---
__Description__ : Return a [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) of the content in the asked type.
__Arguments__
name | type | description
---------|----------|------------
type | String | the type of the result : `string` (or `text`, its alias), `binarystring`, `base64`, `array`, `uint8array`, `arraybuffer`, `nodebuffer`.
onUpdate | Function | an optional function called on each internal update with the metadata.
__Metadata__ : the metadata are :
name | type | description
------------|--------|------------
percent | number | the percent of completion (a double between 0 and 100)
__Returns__ : A [Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) of the content.
__Throws__ : Nothing.
__Example__
```js
zip
.file("my_text.txt")
.async("string")
.then(function success(content) {
// use the content
}, function error(e) {
// handle the error
});
```
```js
zip
.file("my_text.txt")
.async("string", function (meta) {
console.log("Generating the content, we are at " + meta.percent.toFixed(2) + " %");
})
.then(...);
```
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