$ npm -g i @formatjs/cli
$ formatjs extract --help
Usage: formatjs extract [options] [files...]
Usage: formatjs extract [options] [files...]

Extract string messages from React components that use react-intl.
The input language is expected to be TypeScript or ES2017 with JSX.

Options:
  --messages-dir <dir>                                  The target location where the plugin will output a `.json` file corresponding to each component from which React Intl messages were extracted. If not provided, the extracted message
                                                        descriptors will be printed to standard output.
  --out-file <path>                                     The target file path where the plugin will output an aggregated `.json` file of allthe translations from the `files` supplied.
                                                        This flag will ignore --messages-dir
  --id-interpolation-pattern <pattern>                  If certain message descriptors don't have id, this `pattern` will be used to automaticallygenerate IDs for them. Default to `[contenthash:5]`.
                                                        See https://github.com/webpack/loader-utils#interpolatename for sample patterns
  --extract-source-location                             Whether the metadata about the location of the message in the source file should be extracted. If `true`, then `file`, `start`, and `end` fields will exist for each extracted
                                                        message descriptors. (default: false)
  --module-source-name <name>                           The ES6 module source name of the React Intl package. Defaults to: `"react-intl"`, but can be changed to another name/path to React Intl.
  --remove-default-message                              Remove `defaultMessage` field in generated js after extraction (default: false)
  --additional-component-names <comma-separated-names>  Additional component names to extract messages from, e.g: `['FormattedFooBarMessage']`. **NOTE**: By default we check for the fact that `FormattedMessage` is imported from
                                                        `moduleSourceName` to make sure variable alias works. This option does not do that so it's less safe.
  --extract-from-format-message-call                    Opt-in to extract from `intl.formatMessage` call with the same restrictions, e.g: has to be called with object literal such as `intl.formatMessage({ id: 'foo', defaultMessage:
                                                        'bar', description: 'baz'})` (default: false)
  --output-empty-json                                   Output file with empty [] if src has no messages. For build systems like bazel that relies on specific output mapping, not writing out a file can cause issues. (default: false)
  --ignore <files>                                      List of glob paths to **not** extract translations from.
  --throws                                              Whether to throw an exception when we fail to process any file in the batch.
  --pragma <pragma>                                     parse specific additional custom pragma. This allows you to tag certain file with metadata such as `project`. For example with this file:

        ```
        // @intl-meta project:my-custom-project
        import {FormattedMessage} from 'react-intl';

        <FormattedMessage defaultMessage="foo" id="bar" />;
        ```

        and with option `{pragma: "@intl-meta"}`, we'll parse out `// @intl-meta project:my-custom-project` into `{project: 'my-custom-project'}` in the result file.
  -h, --help                                            display help for command