AWS API Gateway No 'Access-Control-Allow-Origin' header is present
<p>I'm stuck on an issue with API gateway and I've gone through all the other SO answers on this, AWS forums and have been through their docs but still no joy.</p>

<p>I am trying to setup an API using AWS API gateway which calls a Lambda function which reads/writes to a table in DynamoDB.</p>

<p>The Lambda function to DynamoDB is working. I have created an API in AWS, and created a GET and OPTIONS methods for it. I read AWS does not enforce the OPTIONS for only GET/POST but i was getting a preflight error in my ajax call when there was no OPTIONS method so I added one.</p>

<p>For now just to make progress I am not using an API key or Authorization.
I can successfully call my GET method using POSTMAN, which returns the contents of the DynamoDB table.</p>

<p>But when i try using a JQuery ajax call i get</p>

<pre><code>No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.
</code></pre>

<p>I can see using Chrome dev tools under the network tab, the OPTIONS method returning status 200 and the GET returns status 200 but with the above error.</p>

<p>I have tried enabling CORS on both the OPTIONS and GET methods, have re-deployed the API after every change, have tried the following (<a href="http://enable-cors.org/server_awsapigateway.html" rel="noreferrer">http://enable-cors.org/server_awsapigateway.html</a>) but always get the same error in the console.</p>

<p>I am executing the ajax call from a file on my desktop so origin is null as the page will be deployed to S3 as its a single web page application in JS.</p>

<p>When I enabled CORS on my GET and OPTIONS i can see that Access-Control-Allow-Headers is <code>'Content-Type,X-Amz-Date,Authorization,X-Api-Key,X-Amz-Security-Token'</code> and Access-Control-Allow-Origin* is <code>'*'</code></p>

<p>My Ajax call looks like below. I also tried copying the exact headers POSTMAN uses, which has the Authorization header set (which i have turned off in AWS for now) but i always get the same error above </p>

<pre><code>var awsHeaders = {};
awsHeaders['X-Amz-Date'] = '20161127T171734';

$('#add, #cloud').click(function() {

    $.ajax({

        type: 'GET',
        headers: awsHeaders,
        dataType : "json",
        url: '...',
        success: function (res) {

            console.log('response in GET:');
            console.log(res);

        },
        error: function(data) {
            console.log('in error');
            console.log(data);
        }

    });

});
</code></pre>

<p>Can anyone shed light on what i might be missing?</p>

<p>Many thanks</p>

<p><strong>Update</strong>
See answer below regarding how I solved this as per DigitalKapteain comments - by setting the 'Access-Control-Allow-Origin':'*' header in the response from my Lambda function. I looked for this in the AWS docs but couldn;t find it. This link describes the difference between Lambda and Lambda Proxy and explains what to do when using CORS <a href="https://serverless.com/framework/docs/providers/aws/events/apigateway/" rel="noreferrer">https://serverless.com/framework/docs/providers/aws/events/apigateway/</a> </p>