JSONPath Evaluator

Overview

Test JSONPath expressions against your own JSON with per-match results: every match is listed with its canonical path and value, plus a total match count. The evaluator covers the core RFC-style operator set — child access, quoted keys, recursive descent, wildcards, negative indices, unions, slices, and filter expressions — as you type, entirely offline.

How It Works

Type an expression such as $.store.books[?(@.price < 10)].title, paste your JSON on the left, and each match appears on the right with its path (like $['store']['books'][2]['title']) and JSON value, under a live match count. Copy values puts the JSON array of matched values on your clipboard. The hint line documents the syntax: $ root, .name children, ..name recursive descent, * wildcards, [0] and [-1] indices, [0,2] unions, [1:5:2] slices, [?(...)] filters with == != < <= > >= =~ comparisons and && / ||, and /regex/ tests.

Step-by-Step Usage Guide

1. Paste your JSON document into the left editor.
2. Enter a path — build it up from $ and watch the match count change.
3. Read the per-match list: each row shows the match's path and value.
4. Click Copy values to take all matched values as a JSON array.

Technical Specifications & Standards

The evaluator (src/lib/jsonPath.ts) parses the expression into segments and walks the document breadth-first, carrying a canonical bracketed path for every match so results are self-describing and copyable. Filters evaluate @-relative operands against each candidate: @.price < 10 compares numerically, @.isbn alone is an existence check, and @.name =~ /Lord/ applies a regular expression. Slices follow Python semantics including negative bounds and steps. Errors are distinct from empty results: malformed syntax (an unclosed bracket, an unsupported mixed union) produces an explicit parse error naming the position, while a well-formed path that matches nothing reports zero matches — so a typo and an absent field are never confused.

Targeted Use Cases

• Verifying an accessor path before hardcoding it in application code.
• Extracting all values matching a condition, such as titles of books under $10, with a filter.
• Learning JSONPath syntax — recursive descent, slices, and filters — with instant per-match feedback.
• Pulling one field out of a large response during debugging without reading the whole payload.

Notes & Gotchas

• Start from $ and build the path one segment at a time; the match count shows exactly where it stops matching.
• Prefer quoted bracket segments like $['weird key'] when a key contains spaces, dots, or dashes.
• Remember filters compare @ against literals: @.price < 10 is numeric, @.name =~ /re/ is a regex, and a bare @.prop is an existence test.
• A zero-match result with no error means the path is valid but matched nothing — check spelling and casing.

Frequently Asked Questions