Documentation Grafana k6 Using k6 JavaScript and TypeScript mode

JavaScript compatibility mode

k6 offers two JavaScript compatibility modes:

• Base mode: Only uses native support in k6 and the underlying JavaScript runtime. For k6 v0.53.0 or higher, it has the same functionality as extended apart from the global aliasing.
• Extended mode: Similar to base mode, with an additional alias from global to globalThis for Node.js compatibility. This is the default mode.

After k6 v0.53.0, the only difference between the base and extended modes is that global, the Node.js global variable, is aliased to the value of globalThis.

When running tests, you can change the mode by using the --compatibility-mode option:

Extended mode

By default, k6 uses the --compatibility-mode=extended mode:

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$ k6 run script.js

Base mode

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$ k6 run --compatibility-mode=base script.js

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$ K6_COMPATIBILITY_MODE=base k6 run script.js

Typescript support

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$ k6 run script.ts

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$ k6 run script.ts

k6 uses esbuild to transpile TypeScript (TS) code for all files that have the .ts extension.

TypeScript support is partial as it strips the type information but doesn’t provide type safety.

CommonJS Example

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const http = require('k6/http');
const k6 = require('k6');

module.exports.options = {
  vus: 10,
  duration: '30s',
};

module.exports.default = function () {
  http.get('http://test.k6.io');
  k6.sleep(1);
};

⚠️ About require()

Note that require() is a custom k6 implementation of module loading, which doesn’t behave in the same way as the require() call in Node.js. Specifically, it only handles loading of built-in k6 modules, scripts on the local filesystem, and remote scripts over HTTP(S), but it does not support the Node.js module resolution algorithm.

Bundling with Babel outside of k6

The examples below demonstrate the use of Babel with bundlers like Webpack and Rollup:

• k6-template-es6: Template using Webpack and Babel to bundle k6 tests.
• k6-rollup-example: Example using Rollup and Babel to bundle a testing project.

Read more

• Running large tests: Optimize k6 for better performance.
• k6 Modules: Different options to import modules in k6.
• k6 Archive Command: The k6 archive command bundles all k6 test dependencies into a tar file, which can then be used for execution. It may also reduce the execution startup time.