JavaScript / ECMAScript

Python f-String Expression in JS

Match `{expression}` placeholders inside Python f-strings (or any single-brace template syntax).

Try it in the JS tester →

Pattern

regexJS
\{([^{}]+)\}   (flags: g)

JavaScript / ECMAScript code

jsJavaScript
const re = new RegExp("\\{([^{}]+)\\}", "g");
const input = "f\"Hello {name}, you are {age} years old\"";
const matches = [...input.matchAll(re)];
console.log(matches.map(m => m[0]));

Uses `String.prototype.matchAll` for global iteration (Node 12+ / all modern browsers).

How the pattern works

\{ matches the literal opening brace. ([^{}]+) captures one or more characters that are NOT another brace — this avoids accidentally matching `{{` (the literal-brace escape in f-strings) and prevents nested-brace headaches. \} matches the closing brace.

Examples

Input

f"Hello {name}, you are {age} years old"

Matches

  • {name}
  • {age}

Input

f"Total: {amount:.2f} USD"

Matches

  • {amount:.2f}

Input

f"escaped {{ not a placeholder }}"

No match

—

Same pattern, other engines

Python (re)

Supported

See how this pattern looks (and behaves) in Python's stdlib `re` module.

Go (RE2)

Supported

See how this pattern looks (and behaves) in Go's `regexp` package (RE2 engine).

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