Filecoin-js-signer is a pure Javascript/Typescript library that provides a complete implementation of the Payment Channel actor's methods, enabling the creation of atomic swaps and atomic loans in the Filecoin network. The library includes necessary methods to create, sign, and broadcast messages to send FIL, and interact with Filecoin's built-in actors such as Payment Channel and Multisig. The library was initially created as part of the Filecoin Loans Grant awarded by the Filecoin Foundation in April 2021. At the time of its creation, there were no fully functional signing libraries written in pure Javascript or Typescript, and this library aims to fill that gap. Additionally, a pure Javascript implementation of these methods can simplify the usage from web and mobile applications that interact with the Filecoin network. By providing a comprehensive and functional signing library, Filecoin-js-signer aims to promote broader adoption of the Filecoin network and enable developers to build more complex and secure applications on top of it.