Code & Markup · In-Browser Regular Expression Lab

JSON Key Regex — Extract All Object Keys from JSON Text

Captures all property keys from JSON formatted strings using lookahead for the colon separator.

Pattern:

Regular Expression Pattern & Flags

Flags:

//g

Live Test String

Match Found

Load Sample:

Match Inspection & Details3 matches

Match #1:"id":

Match #2:"name":

Match #3:"active":

Test Samples Verification Matrix

Expected Valid Samples (Should Match)

{"id": 10, "name": "Castov", "active": true} Pass

Expected Invalid Samples (Must Reject)

["value1", "value2"] Rejected (Pass)

Code Implementation Generator

// JavaScript / TypeScript (ES6+)
const pattern = /"([a-zA-Z_][a-zA-Z0-9_]*)"\s*:/g;
const text = "{\"id\": 10, \"name\": \"Castov\", \"active\": true}";

const isMatch = pattern.test(text);
console.log("Is Match:", isMatch);

if (isMatch) {
  const matches = text.match(pattern);
  console.log("Matches:", matches);
}

Regular Expression Token Breakdown

Matches double-quoted identifier strings followed immediately by a colon. Each component of the regular expression serves a distinct syntactical purpose as mapped below:

Token Pattern	Name / Component	Function & Rule
"	Opening quote	Literal double quote.
([a-zA-Z_][a-zA-Z0-9_]*)	Key Identifier	Captures standard property key.
"\s*:	Colon separator	Trailing quote and JSON key delimiter.