JavaScript Array Replacements Resolver

Array-based string replacement is one of the most common JavaScript obfuscation techniques. It works by storing all string literals (function names, messages, URLs, etc.) in one or more arrays indexed by numeric keys. The original strings are then accessed via array index expressions like _0x1234[0] instead of the literal strings themselves. This technique makes it much harder for static analysis tools and human readers to understand what the code does, since meaningful strings like "https://api.example.com" become cryptic expressions like_0xabcd[42].

Our resolver uses a three-step process to deobfuscate array-based string replacements:

1. Array Detection: Scans the input code for variable declarations that contain arrays of string values (e.g., var _0x = ["Hello", "World"]). Identifies all such string storage arrays and their contents.
2. Access Resolution: Finds all expressions where these arrays are accessed using bracket notation (e.g., _0x[0]). Evaluates the index expression to a numeric value and looks up the corresponding string from the array. Supports direct numbers, hex (0xFF), binary (0b1010), octal (0o77), and simple arithmetic expressions.
3. Inline Replacement: Replaces each array access expression with the resolved string literal, and optionally removes the original array declarations from the output. A complete mapping table shows every replacement made.

Array-based string replacement is easy to spot once you know what to look for. Common indicators include variable declarations containing arrays of seemingly random strings, frequent bracket access patterns like _0x1234[0] or _0xabc["length"], and variable names that look like hex numbers (e.g., _0xabcd,_0x1234). Many popular obfuscators use this technique, including javascript-obfuscator, JScrambler, and various custom packers. The number of strings per array can range from a few to several hundred, often spanning multiple arrays to make analysis harder.

While our resolver handles the most common array replacement patterns, some advanced obfuscators use techniques that can defeat simple detection. These include dynamically building arrays at runtime, using computed property access with complex expressions, splitting strings across multiple array entries, or using nested function calls to obscure array accesses. For best results, combine this tool with other deobfuscation techniques like beautification, variable name analysis, and manual code inspection. Always verify the resolved output in a sandboxed environment before using it for security analysis.