# JavaScript Evaluation

Use `eval` to run JavaScript in the browser context.

Simple expressions can use regular shell quoting:

```bash
agent-browser eval 'document.title'
agent-browser eval 'document.querySelectorAll("img").length'
```

For complex JavaScript, use `--stdin` to avoid shell quoting corruption:

```bash
agent-browser eval --stdin <<'EVALEOF'
JSON.stringify(
  Array.from(document.querySelectorAll("img"))
    .filter(i => !i.alt)
    .map(i => ({ src: i.src.split("/").pop(), width: i.width }))
)
EVALEOF
```

Use base64 for generated scripts:

```bash
agent-browser eval -b "$(printf '%s' 'Array.from(document.querySelectorAll("a")).map(a => a.href)' | base64)"
```

Rules of thumb:

- Single-line with no nested quotes: regular `eval 'expression'`.
- Nested quotes, arrow functions, template literals, or multiline: `eval --stdin`.
- Programmatic scripts: `eval -b`.