skills/agent-browser/references/eval.md

JavaScript Evaluation

Use eval to run JavaScript in the browser context.

Simple expressions can use regular shell quoting:

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

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

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:

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.