user.js

amazon_reviewmeta.user.js

// ==UserScript==
// @name         ReviewMeta Amazon Search
// @namespace    http://tampermonkey.net/
// @version      0.1.6
// @description  Modify star ratings on Amazon pages based on ReviewMeta scores
// @author       bhughes339
// @include      https://*.amazon.tld/*
// @grant        none
// @require      http://code.jquery.com/jquery-latest.js
// ==/UserScript==

/* Color legend:
   Green - Pass (good)
   Yellow - Warn (iffy)
   Red - Fail (bad)
   Grey - Not yet analyzed by ReviewMeta */

   (function() {
    'use strict';

    function getClassFromScore(score) {
        score = parseFloat(score);
        var rounded = (Math.round(score * 2) / 2).toString();
        return `a-star-${rounded.replace('.', '-')}`;
    }

    function modStars(asin, ele) {
        $.getJSON('https://reviewmeta.com/api/amazon/' + asin, function(data) {
            switch (data.s_overall) {
                case "1":
                    ele.attr('style', 'filter:hue-rotate(40deg)');
                    break;
                case "2":
                    ele.attr('style', 'filter:hue-rotate(380deg)');
                    break;
                case "3":
                    ele.attr('style', 'filter:hue-rotate(315deg) saturate(500%)');
                    break;
                default:
                    ele.attr('style', 'filter:grayscale(100%)');
                    ele.attr('onclick', `window.open('${data.href}');`);
                    break;
            }
            // ele.append(` (${data.rating})`);
            if (data.rating) {
                var classes = `a-icon a-icon-star ${getClassFromScore(data.rating)}`;
                ele.find('i').removeClass(function(index, className) {
                    return (className.match(/a-star(?:[\S]*)?-[\d-]+/) || []).join(' ');
                }).addClass(getClassFromScore(data.rating));
                var ratingSpan = document.querySelector("#averageCustomerReviews span.a-size-base");
                if (ratingSpan) {
                    if (ratingSpan.innerText.length < 5) {
                        ratingSpan.innerText += `(${data.rating}) `;
                    }
                }
            }
        });
    }

    // Get the ASIN from the data-a-popover attribute of a span item
    function getAsinFromSpan(ele) {
        var popover = ele.attr('data-a-popover');
        if (typeof popover === 'string') {
            var asin = popover.match(/asin=([A-Za-z\d]+)/);
            if (asin) {
                return asin[1];
            }
        }
        return null;
    }

    var url = window.location.href;
    var asinMatch = url.match(/\/(B[\dA-Z]{9}|\d{9}(?:X|\d))/); // https://stackoverflow.com/questions/2123131/determine-if-10-digit-string-is-valid-amazon-asin
    var srch = (asinMatch) ? 'span#acrPopover' : 'span.a-declarative';
    $(srch).each(function(index) {
        var $self = $(this);
        var asin = (asinMatch) ? asinMatch[1] : getAsinFromSpan($self);
        if (asin) {
            modStars(asin, $self);
        }
    });
})();

Would you mind replacing the @match .com with @include .tld? That way all Versions of Amazon (.com, .de, .fr, .es, ....) could use your Script!

You'd just have to change
// @match https://*.amazon.com/s/*
to
// @include https://*.amazon.tld/s/*

Regards and thanks for this nice script!

@wsoyka Thanks for the suggestion! I made the change to the script.

hola

Any chance you could change the orange on the "warn" grade to yellow or something else?

Amazon now colors its star ratings orange, so for items with warn grades you can't tell if you're looking at the original Amazon rating or the modified ReviewMeta rating. The other colors don't quite match ReviewMeta's either (the green is really pale and the red comes out pink) but at least those are different from Amazon's.

If it helps, ReviewMeta uses these:
Pass - #009e0f (green)
Warn - #f8f850 (yellow)
Fail - #cf2a27 (red)

EDIT: Just noticed you updated this with v0.1.5. Looks good -- thanks!