Use the proper transformers for specific `dataType` and `responseType` values.

Implement and document proper transformation of request and response body according to dataType and responseType options.

This will fix: #375, #448, #765, #793

[Scriptim]

https://github.com/axios/axios/blob/6642ca9aa1efae47b1a9d3ce3adc98416318661c/lib/defaults.js#L57-L65

I really don’t think that the current default parsing behavior is sensible.

It may even cause the data to be altered under certain circumstances, e. g.: Let’s say a server sends a 16 character string (with according header) of digits: 4201172030730738. The default behavior would convert this to the integer value 4201172030730738, although this is obviously not a JSON object (even if it is a valid JSON value). In case the string is e.g. 9100000000000001 (i.e. > Number.MAX_SAFE_INTEGER), parsing will cause the value to be changed to 9100000000000000 due to inaccuracy of the float data type.

This is not a far-fetched example, but rather a problem that has really occurred and has required quite a bit of debugging. Especially since this is not adequately documented in my opinion.

I suggest that parsing to JSON is only done if the data is really in JSON format, i. e. the Content-Type header is set to application/json and/or the value of dataType/responseType is set accordingly.

[scudette]

Jut hit this bug as well but I did find a workaround which seems to work for me so might save someone else some time:

axios({
        responseType: 'blob',
        method: 'get',
        url: url,
        params: params,
 }).then((response) => response.data.text()};