# Create functions
<a name="create-function"></a>

You create a function in two stages: 

1. Create the function code as JavaScript. You can use the default example from the CloudFront console or write your own. For more information, see the following topics:
   + [Write function code](writing-function-code.md)
   + [CloudFront Functions event structure](functions-event-structure.md)
   + [CloudFront Functions examples for CloudFront](service_code_examples_cloudfront_functions_examples.md)

1. Use CloudFront to create the function and include your code. The code exists inside the function (not as a reference).

------
#### [ Console ]

**To create a function**

1. Sign in to the CloudFront console at [https://console.amazonaws.cn/cloudfront/v4/home#/functions](https://console.amazonaws.cn/cloudfront/v4/home#/functions) and choose the **Functions** page.

1. Choose **Create function**.

1. Enter a function name that is unique within the Amazon Web Services account, choose the JavaScript version, and then choose **Continue**. The details page for the new function appears.
**Note**  
To use [key-value pairs](kvs-with-functions.md) in the function, you must choose JavaScript runtime 2.0.

1. In the **Function code** section, choose the **Build ** tab and enter your function code. The sample code that is included in the **Build** tab illustrates the basic syntax for the function code.

1. Choose **Save changes**.

1. If the function code uses key-value pairs, you must associate a key value store. 

   You can associate the key value store when you first create the function. Or, you can associate it later, by [updating the function](update-function.md). 

   To associate a key value store now, follow these steps:
   + Go to the **Associate KeyValueStore** section and choose **Associate existing KeyValueStore**.
   + Select the key value store that contains the key-value pairs in the function, and then choose **Associate KeyValueStore**.

   CloudFront immediately associates the store with the function. You don't need to save the function.

------
#### [ CLI ]

If you use the CLI, you typically first create the function code in a file, and then create the function with the Amazon CLI.

**To create a function**

1. Create the function code in a file, and store it in a directory that your computer can connect to. 

1. Run the command as shown in the example. This example uses the `fileb://` notation to pass in the file. It also includes line breaks to make the command more readable. 

   ```
   aws cloudfront create-function \
       --name MaxAge \
       --function-config '{"Comment":"Max Age 2 years","Runtime":"cloudfront-js-2.0","KeyValueStoreAssociations":{"Quantity":1,"Items":[{"KeyValueStoreARN":"arn:aws:cloudfront::111122223333:key-value-store/a1b2c3d4-5678-90ab-cdef-EXAMPLE11111"}]}}' \
       --function-code fileb://function-max-age-v1.js
   ```
**Notes**  
`Runtime` – The version of JavaScript. To use [key value pairs](kvs-with-functions.md) in the function, you must specify version 2.0.
`KeyValueStoreAssociations` – If your function uses key-value pairs, you can associate the key value store when you first create the function. Or, you can associate it later, by using `update-function`. The `Quantity` is always `1` because each function can have only one key value store associated with it.

   When the command is successful, you see output like the following.

   ```
   ETag: ETVABCEXAMPLE
   FunctionSummary:
     FunctionConfig:
       Comment: Max Age 2 years
       Runtime: cloudfront-js-2.0
       KeyValueStoreAssociations= \
         {Quantity=1, \
         Items=[{KeyValueStoreARN='arn:aws:cloudfront::111122223333:key-value-store/a1b2c3d4-5678-90ab-cdef-EXAMPLE11111'}]} \
     FunctionMetadata:
       CreatedTime: '2021-04-18T20:38:56.915000+00:00'
       FunctionARN: arn:aws:cloudfront::111122223333:function/MaxAge
       LastModifiedTime: '2023-11-19T20:38:56.915000+00:00'
       Stage: DEVELOPMENT
     Name: MaxAge
     Status: UNPUBLISHED
   Location: https://cloudfront.amazonaws.com/2020-05-31/function/arn:aws:cloudfront:::function/MaxAge
   ```

   Most of the information is repeated from the request. Other information is added by CloudFront.
**Notes**  
`ETag` – This value changes each time you modify the key value store. You use this value and the function name to reference the function in the future. Make sure that you always use the current `ETag`.
`FunctionARN` – The ARN for your CloudFront function.
111122223333 – The Amazon Web Services account.
`Stage` – The stage of the function (`LIVE` or `DEVELOPMENT`). 
`Status` – The status of the function (`PUBLISHED` or `UNPUBLISHED`).

------

After you create the function, it's added to the `DEVELOPMENT` stage. We recommend that you [test your function](test-function.md) before you [publish it](publish-function.md). After you publish your function, the function changes to the `LIVE` stage.