Origin Request Trigger for lambda@edge supporting nice-urls

index.js

'use strict';
exports.handler = (event, context, callback) => {
    // Extract the request from the CloudFront event that is sent to Lambda@Edge 
    const request = event.Records[0].cf.request;

    // Extract the URI from the request
    const olduri = request.uri;
    const [path, query] = olduri.split('?');
    
    let redirecturi = null;
    let originuri = null;
    
    if (/\/index\.html$/.test(path)) {
        // disallow index.html suffixes
        redirecturi = path.substring(0, path.length - 11);
        if (redirecturi === '') {
            redirecturi = '/'
        }
    } else if (/\/[^/.]+\/$/.test(path)) {
        // if it ends in a slash, remove it 
        redirecturi = path.substring(0, path.length - 1);
    } else if (/\/[^/.]+$/.test(path)) {
        originuri = path + '\/index.html';
    } else if (path === '' || path === '/') {
        originuri = '\/index.html';
    }
   
    // Log the URI as received by CloudFront and the new URI to be used to fetch from origin
    console.log("Request URI: " + olduri);

    if (redirecturi) {
        redirecturi += (query ? `?{query}` : '') ;
        console.log("Redirect URI: " + redirecturi); 

        return callback(null, {
            status: 301,
            headers: {
                location: [{ key: 'Location', value: redirecturi }],
            },
        });
    }

    if (originuri) {
        originuri += (query ? `?{query}` : '');
        
        request.uri = originuri;
    }
   
    console.log("Origin URI: " + request.uri);
    return callback(null, request);

};

Don't forget to add IAM permissions for your new Lambda function

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": [
                "lambda:GetFunction",
                "lambda:EnableReplication"
            ],
            "Resource": "arn:aws:lambda:us-east-1:xxxxxxxxxxx:function:cloudfront-nice-urls:1"
        },
        {
            "Sid": "VisualEditor1",
            "Effect": "Allow",
            "Action": [
                "iam:CreateServiceLinkedRole",
                "cloudfront:UpdateDistribution"
            ],
            "Resource": "*"
        }
    ]
}

And then add Trust Relationship

{
   "Version": "2012-10-17",
   "Statement": [
      {
         "Effect": "Allow",
         "Principal": {
            "Service": [
               "lambda.amazonaws.com",
               "edgelambda.amazonaws.com"
            ]
         },
         "Action": "sts:AssumeRole"
      }
   ]
}