Unaudited Condensed Statements of Stockholders Equity (Parenthetical) $ in Thousands	3 Months Ended
Mar. 31, 2024 USD ($)
Statement of Stockholders' Equity [Abstract]
Issuance costs	$ 20,896

Common stock and pre-funded warrants issuance costs.

No definition available.

Name:	janx_CommonStockAndPreFundedWarrantsIssuanceCosts
Namespace Prefix:	janx_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration