JSON Map Reduce Tool – Transform JSON Arrays
Apply map and reduce style transformations to JSON arrays online. Our free JSON Map Reduce Tool helps developers test data transformations quickly without a full code setup.
About JSON Map Reduce Tool
Transforming JSON arrays usually requires writing JavaScript code. This tool lets you apply map and reduce operations directly in the browser, testing transformations before adding them to your codebase.
How it works
Paste a JSON array and write a map function using JavaScript arrow syntax. Optionally add a reduce function to aggregate results. Click Execute to see the transformation.
Use the Quick Presets for common operations like extracting properties, summing values, or counting items. The result appears below, ready to copy or download.
When you'd use this
You need to transform API data before displaying it. Test your map/reduce logic here first to verify it produces the expected output before deploying.
This executes JavaScript in your browser, which has security implications. Don't use with untrusted input. For production, implement transformations in your actual code.
Questions
What syntax do map functions use?
Use arrow function syntax like "item => item.name" or "item => ({ id: item.id, total: item.price * item.quantity })".
Is the reduce function required?
No, reduce is optional. Without it, the result is the mapped array. With it, you get a single aggregated value.
What parameters are available?
Map receives (item, index, arr). Reduce receives (acc, item, index, arr). Use these to access data and context.
Can I chain multiple operations?
Not directly. Run one operation, copy the result, and paste it as new input for the next transformation step.
What if my function has an error?
An error message appears describing the issue. Check your syntax and ensure you're accessing valid properties.