What file formats can I paste from?

You can paste from Excel (tab-separated), CSV files (comma-separated), text files with pipes or spaces. The delimiter is automatically detected. For best results, copy directly from Excel.

What happens if my data has 3 or more columns?

Only the first two columns are used (key and value). Extra columns are ignored. If your key or value contains tabs/commas, use a different delimiter or manually adjust the data.

Can I convert data with special characters or quotes?

Yes. The tool automatically escapes quotes, backslashes, newlines, and tabs according to each programming language's syntax. Your generated code is safe to use.

Why do I see a yellow warning banner?

Yellow warnings appear when: (1) Duplicate keys are detected (last occurrence is kept), or (2) Dataset exceeds 10,000 rows (still converted, but may be slow).

Why do I see a red error message?

Red errors occur when: (1) Empty keys are found (keys must be non-empty), (2) Dataset exceeds 50,000 rows (too large to convert), or (3) Input is completely empty.

How do I convert from code back to Excel?

This tool is one-way (Excel → Code). To convert code back to Excel, use a JSON-to-CSV converter or manually reformat the code.

Is my data sent to a server?

No. All conversion is performed entirely in your browser using JavaScript. Your data is never transmitted to or stored on any server.

Can I save the generated code to a file?

Click the 'Copy Code' button to copy the code to your clipboard. Then paste it into your code editor and save as a .json, .py, .php, .js, .ts, .rb, or .java file.

Key-Value Mapper

Convert 2-column data to Map/Dictionary code formats

Free online tool that converts 2-column Excel data (keys and values) to Map/Dictionary code formats. Supports JSON, Python, PHP, JavaScript, TypeScript, Ruby, Java, and more. All processing is done in your browser, no data is stored.

How to Use

Convert in 3 simple steps:

Paste 2-Column Data

Copy 2-column data (e.g., country code and name) from Excel and paste into the input area. Tab, comma, pipe, or space delimiters are automatically detected.

Select Output Format

Choose your desired programming language format from the dropdown (JSON, Python, PHP, JavaScript, TypeScript, Ruby, Java).

Copy the Code

The code is generated in real-time. Click the 'Copy' button to copy the Map/Dictionary code to your clipboard and paste it directly into your program.

Privacy Protection: All conversion is performed in your browser. Your data is not sent or stored on any server.

Key-Value Mapper

Output Format

Input Data (2 columns: Key and Value)

Generated Code

Practical Use Cases

Key-Value Mapper is useful in various data engineering and development scenarios:

Hardcoding Master Data

When you need to hardcode reference tables (country codes, currency codes, status names, etc.) from Excel into your program as constants.

Configuration Code Generation

Convert configuration tables (environment variables, feature flags, error code mappings) to code format for quick integration.

Test Data Preparation

Generate test fixtures and mock data from Excel sheets in your preferred programming language format.

Data Migration Scripts

When migrating data between systems, convert mapping tables from Excel to code for transformation logic.

Enum-like Constant Definitions

Create lookup tables or enum-like structures from ID-name pairs in your codebase.

Translation Dictionary Setup

Convert language translation pairs from Excel to JSON or code format for internationalization (i18n) configuration.

What is a Key-Value Map (Associative Array)?

A key-value map (also called associative array, dictionary, hash, or object) is a fundamental data structure that stores pairs of keys and their associated values. Unlike simple lists, maps allow you to retrieve values using meaningful keys instead of numeric indices.

Basic Structure

Each entry consists of a unique key and its corresponding value. For example, mapping country codes (keys) to country names (values): 'JP' → 'Japan', 'US' → 'United States'.

Advantages of Maps

Semantic access: Retrieve data using meaningful keys (e.g., config['database_host']) instead of array indices
Fast lookups: Most implementations provide O(1) average-case lookup time
Flexible keys: Use strings, numbers, or even objects as keys (language-dependent)
Self-documenting: Code becomes more readable when using descriptive keys

Implementation in Programming Languages

Python: dict type - {'key': 'value'}
JavaScript: Object or Map - {key: 'value'} or new Map()
PHP: Associative array - ['key' => 'value']
Java: HashMap or Map interface - new HashMap<>() with put(key, value)
Ruby: Hash - {key: 'value'} or Hash.new
TypeScript: Record or Map - Record<string, string> or Map<K, V>

Tips and Best Practices

Delimiter Detection

The tool automatically detects delimiters in this priority order: Tab > Comma > Pipe (|) > Space. For best results, copy directly from Excel (tab-separated) or use comma-separated values.

Duplicate Keys

If your data contains duplicate keys, the tool will keep the last occurrence and display a yellow warning banner with the list of duplicates.

Empty Keys and Values

Empty keys will cause an error (keys must be unique and non-empty). Empty values are allowed. Completely blank lines are silently skipped.

Row Limits

Yellow warning at 10,000 rows (large dataset). Red error at 50,000 rows (too large, conversion rejected). For typical master data (< 1,000 rows), conversion is instant.

Quote Escaping

The tool automatically escapes special characters (quotes, backslashes, newlines) according to each language's syntax rules. Your generated code is safe to paste directly.

Real-Time Conversion

Conversion starts automatically 300ms after you stop typing (debounced). No need to click a 'Convert' button—just paste and select your format.

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Related Tools

Other useful data conversion and formatting tools: