karatelabs/karate · error · Error

Unable to resolve global `this`

Error message

Unable to resolve global `this`

What it means

resemble.js needs a reference to the JS global object to function, and this fallback resolver checks `self` and `window` before giving up. It throws when the script runs in a non-DOM environment (e.g. a bare Node worker, older runtime without globalThis) where neither global exists. It indicates the environment cannot host this browser-oriented library.

Solutions

1. Run in a real browser context or update Node to >= 12 so `globalThis` exists
2. Polyfill the global before loading: `(0,eval)('this').globalThis = ...` or use a shim like `global-this`
3. Do not import resemble.js in server-side code; use a JVM/native image-diff library instead

Example fix

// before (Node 10, no globalThis/window/self)
require('./resemble.js');
// after
if (typeof globalThis === 'undefined') { globalThis = require('global-this'); }
require('./resemble.js');

When it happens

Trigger: Loading resemble.js in an environment where `self`, `window`, and `globalThis` are all undefined — e.g. a plain Node < 12 runtime, a web worker context stripped of globals, or server-side evaluation of the static asset.

Common situations: Serving karate-ext static assets into a Node-based screenshot/diff runner on an old Node version; bundling resemble.js for server-side use instead of browser use.

Understand the failure class

Background: "unsupported platform" / "not supported on this platform" errors: what they mean and how to fix them — this error's family across 47 libraries.

Related errors

• Invalid ignore
• karate-boot.js evaluation failed
• Dynamic expression must return a list or function
• Failed to evaluate dynamic expression
• doc() requires 'read' key with template path

AI-assisted analysis of karatelabs/karate@a22eb90246 (2026-09-12). Data as JSON: /api/errors/51c55b233b4af169. Report an issue: GitHub.

Appendix: source

Thrown at karate-image/src/main/resources/META-INF/karate-ext/static/resemble.js:14

/*
James Cryer / Huddle
URL: https://github.com/Huddle/Resemble.js
*/

var naiveFallback = function () {
    // ISC (c) 2011-2019 https://github.com/medikoo/es5-ext/blob/master/global.js
    if (typeof self === "object" && self) {
        return self;
    }
    if (typeof window === "object" && window) {
        return window;
    }
    throw new Error("Unable to resolve global `this`");
};

var getGlobalThis = function () {
    // ISC (c) 2011-2019 https://github.com/medikoo/es5-ext/blob/master/global.js
    // Fallback to standard globalThis if available
    if (typeof globalThis === "object" && globalThis) {
        return globalThis;
    }

    try {
        Object.defineProperty(Object.prototype, "__global__", {
            get: function () {
                return this;
            },
            configurable: true
        });
    } catch (error) {
        return naiveFallback();

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