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eval

Evaluate a JavaScript expression in the Tauri app's webview.

Bridge Required

This command requires an active bridge connection.

Usage

tauri-agent-tools eval [expression] [options]

Options

Option Description Default
[expression] JavaScript expression; choose this or --file —
--file <path> Read JavaScript from a file —
--json Output { "result": value } with the evaluated value —
--port <number> Bridge port (auto-discover if omitted) —
--token <string> Bridge token (auto-discover if omitted) —
--pid <number> Select an app bridge by PID —
--window-label <label> Select a webview main

Examples

Get document title

tauri-agent-tools eval "document.title"

My Tauri App

Count elements

tauri-agent-tools eval "document.querySelectorAll('.item').length"

42

Get structured data

tauri-agent-tools eval "JSON.stringify({url: location.href, ready: document.readyState})"

{
  "url": "http://localhost:1420/",
  "ready": "complete"
}

Check Tauri API availability

tauri-agent-tools eval "!!(window.__TAURI_INTERNALS__ || window.__TAURI__)"

true

Get computed style value

tauri-agent-tools eval "getComputedStyle(document.querySelector('.btn')).backgroundColor"

Notes

  • The expression runs in the webview's JavaScript context
  • Results that look like JSON are automatically pretty-printed
  • The bridge has a 5-second timeout per evaluation
  • JavaScript runs in the selected webview’s global context and can modify application state
  • Promises are awaited; thrown exceptions fail the command, while a literal string beginning with ERROR: remains a successful result
  • --json returns typed JSON values; undefined becomes null, and top-level BigInts, symbols, functions, and non-finite numbers become strings
  • Fatal errors use the shared JSON error envelope on stderr when --json is supplied

Structured and file-based evaluation

tauri-agent-tools eval 'Promise.resolve({ready: true})' --json
# { "result": { "ready": true } }
tauri-agent-tools eval --file inspect.js --window-label settings --json

Supply either an expression or --file, not both.