js-apis-system-fetch.md

# @system.fetch (Data Request)

> **NOTE**
> - The APIs of this module are no longer maintained since API version 6. You are advised to use [`@ohos.net.http`](js-apis-http.md) instead.
> 
> - The initial APIs of this module are supported since API version 3. Newly added APIs will be marked with a superscript to indicate their earliest API version.


## Modules to Import


```
import fetch from '@system.fetch';
```


## fetch.fetch<sup>3+</sup>

fetch(Object): void

Obtains data through a network.

**System capability**: SystemCapability.Communication.NetStack

**Parameters**
| Name| Type| Mandatory| Description|
| -------- | -------- | -------- | -------- |
| url | string | Yes| Resource URL.|
| data | string \| Object | No| Request parameter, which can be a string or a JSON object. For details, see the mapping between **data** and **Content-Type**.|
| header | Object | No| Request header.|
| method | string | No| Request method. The default value is **GET**. The value can be **OPTIONS**, **GET**, **HEAD**, **POST**, **PUT**, **DELETE **or **TRACE**.|
| responseType | string | No| Response type. The return type can be text or JSON. By default, the return type is determined based on **Content-Type** in the header returned by the server. For details, see return values in the **success** callback.|
| success | Function | No| Called when the API call is successful. The return value is defined by [FetchResponse](#fetchresponse).|
| fail | Function | No| Called when API call has failed.|
| complete | Function | No| Called when the API call is complete.|

**Table 1** Mapping between data and Content-Type

| data | Content-Type | Description|
| -------- | -------- | -------- |
| string | Not set| The default value of Content-Type is **text/plain**, and the value of data is used as the request body.|
| string | Any type| The value of data is used as the request body.|
| Object | Not set| The default value of **Content-Type** is **application/x-www-form-urlencoded**. The **data** value is encoded based on the URL rule and appended in the request body.|
| Object | application/x-www-form-urlencoded | The value of data is encoded based on the URL rule and is used as the request body.|

## FetchResponse

| Name| Type| Readable| Writable| Description|
| -------- | -------- | -------- | -------- | -------- |
| code | number | Yes| No| Server status code.|
| data | string \| Object | Yes| No| The type of the returned data is determined by **responseType**. For details, see the mapping between **responseType** and **data** in **success** callback.|
| headers | Object | Yes| No| All headers in the response from the server.|

**Table 2** Mapping between responseType and data in success callback

| responseType | data | Description|
| -------- | -------- | -------- |
| N/A| string | When the type in the header returned by the server is **text/\***, **application/json**, **application/javascript**, or **application/xml**, the value is the text content.|
| text | string | Text content.|
| json | Object | A JSON object.|

**Example**

```
export default {
  data: {
    responseData: 'NA',
    url: "test_url",
  },
  fetch: function () {
    var that = this;
    fetch.fetch({
      url: that.url,
      success: function(response) {
        console.info("fetch success");
        that.responseData = JSON.stringify(response);
      },
      fail: function() {
        console.info("fetch fail");
      }
    });
  }
}
```


> **NOTE**
>   HTTPS is supported by default. To support HTTP, you need to add **"network"** to the **config.json** file, and set the attribute **"cleartextTraffic"** to **true**. That is:
>   
> ```
> {
>   "deviceConfig": {
>     "default": {
>       "network": {
>         "cleartextTraffic": true
>       }
>       ...
>     }
>   }
>   ...
> }
> ```