Magento 2 ajax success json error

Question

I'm trying to to an ajax call using following code

$.ajax({
                    type: 'POST'
                    ,url: SOME_URL
                    ,data: {testdata : testid}
                    ,success: function(result){
                     //code
                    }});

SOME_URL points to a controller file having following code.

public function execute()
{

echo '{"test":["-1.00","-2.00"]}';

}

when I debug the success function of ajax call I get data in the result variable of success function parameter.

"{"test":["-1.00","-2.00"]}exception 'Exception' with message 'Warning: Cannot modify header information - headers already sent by (output started at /Applications/MAMP/htdocs/magentoce21/app/code/<<company>>/<<route_name>>/Controller/Index/View.php:58) in /Applications/MAMP/htdocs/magentoce21/vendor/magento/framework/Stdlib/Cookie/PhpCookieManager.php on line 126' in /Applications/MAMP/htdocs/magentoce21/vendor/magento/framework/App/ErrorHandler.php:61
Stack trace:
#0 [internal function]: Magento\Framework\App\ErrorHandler->handler(2, 'Cannot modify h...', '/Applications/M...', 126, Array)
#1 /Applications/MAMP/htdocs/magentoce21/vendor/magento/framework/Stdlib/Cookie/PhpCookieManager.php(126): setcookie('X-Magento-Vary', '252f89d2ca7ad02...', 0, '/', '', false, true)
#2 /Applications/MAMP/htdocs/magentoce21/vendor/magento/framework/Stdlib/Cookie/PhpCookieManager.php(78): Magento\Framework\Stdlib\Cookie\PhpCookieManager->setCookie('X-Magento-Vary', '252f89d2ca7ad02...', Array)
#3 /Applications/MAMP/htdocs/magentoce21/vendor/magento/framework/App/Response/Http.php(85): Magento\Framework\Stdlib\Cookie\PhpCookieManager->setSensitiveCookie('X-Magento-Vary', '252f89d2ca7ad02...', Object(Magento\Framework\Stdlib\Cookie\SensitiveCookieMetadata))
#4 /Applications/MAMP/htdocs/magentoce21/var/generation/Magento/Framework/App/Response/Http/Interceptor.php(37): Magento\Framework\App\Response\Http->sendVary()
#5 /Applications/MAMP/htdocs/magentoce21/vendor/magento/module-page-cache/Model/App/Response/HttpPlugin.php(25): Magento\Framework\App\Response\Http\Interceptor->sendVary()
#6 /Applications/MAMP/htdocs/magentoce21/vendor/magento/framework/Interception/Interceptor.php(123): Magento\PageCache\Model\App\Response\HttpPlugin->beforeSendResponse(Object(Magento\Framework\App\Response\Http\Interceptor))
#7 /Applications/MAMP/htdocs/magentoce21/var/generation/Magento/Framework/App/Response/Http/Interceptor.php(117): Magento\Framework\App\Response\Http\Interceptor->___callPlugins('sendResponse', Array, Array)
#8 /Applications/MAMP/htdocs/magentoce21/vendor/magento/framework/App/Http.php(185): Magento\Framework\App\Response\Http\Interceptor->sendResponse()
#9 /Applications/MAMP/htdocs/magentoce21/vendor/magento/framework/App/Http.php(156): Magento\Framework\App\Http->handleDeveloperMode(Object(Magento\Framework\App\Bootstrap), Object(Exception))
#10 /Applications/MAMP/htdocs/magentoce21/vendor/magento/framework/App/Bootstrap.php(263): Magento\Framework\App\Http->catchException(Object(Magento\Framework\App\Bootstrap), Object(Exception))
#11 /Applications/MAMP/htdocs/magentoce21/index.php(52): Magento\Framework\App\Bootstrap->run(Object(Magento\Framework\App\Http))
#12 {main}"

I checked for any white-spacing in the php code, but found none.

Answer 1

Try the following -:

public function execute()  
{      
   echo '{"test":["-1.00","-2.00"]}';
   die();
}

Answer 2

Your public function execute() should return 'foobar', not echo 'foobar'.

By echoing it immediately you're throwing everything off hence the headers already sent by (output started

Replace

public function execute()
{

echo '{"test":["-1.00","-2.00"]}';

}

with

public function execute()
{
    return'{"test":["-1.00","-2.00"]}';
}

Or, to be extra fancy:

public function execute()
{
    return json_encode(['test' => [-1, -2]]);
}