dist/vue-resource.esm.js
function json (request) {

    var type = request.headers.get('Content-Type') || '';

    if (isObject(request.body) && type.indexOf('application/json') === 0) {
        request.body = JSON.stringify(request.body);
    }

    return function (response) {

        return response.bodyText ? when(response.text(), function (text) {

            var type = response.headers.get('Content-Type') || '';

            if (type.indexOf('application/json') === 0 || isJson(text)) {

                try {
                    response.body = JSON.parse(text);
                } catch (e) {
                    response.body = null;
                }

            } else {
                response.body = text;
            }

            return response;

        }) : response;

    };
}
function json (request) {

    var type = request.headers.get('Content-Type') || '';

    if (isObject(request.body) && type.indexOf('application/json') === 0) {
        request.body = JSON.stringify(request.body);
    }

    return function (response) {

        return response.bodyText ? when(response.text(), function (text) {

            var type = response.headers.get('Content-Type') || '';

            if (type.indexOf('application/json') === 0 || isJson(text)) {

                try {
                    response.body = JSON.parse(text);
                } catch (e) {
                    response.body = null;
                }

            } else {
                response.body = text;
            }

            return response;

        }) : response;

    };
}
function json ( request ) { var type = request . headers . get ( 'Content-Type' ) || '' ; if ( isObject ( request . body ) && type . indexOf ( 'application/json' ) === 0 ) { request . body = JSON . stringify ( request . body ) ; } return function ( response ) { return response . bodyText ? when ( response . text ( ) , function ( text ) { var type = response . headers . get ( 'Content-Type' ) || '' ; if ( type . indexOf ( 'application/json' ) === 0 || isJson ( text ) ) { try { response . body = JSON . parse ( text ) ; } catch ( e ) { response . body = null ; } } else { response . body = text ; } return response ; } ) : response ; } ; }
JSON Interceptor.
JSON Interceptor .