es-toolkit: How a Small Internal Library Became a Global Project

There was a need for a library that provides functions commonly used in frontend development, such as throttle, debounce, and uniq. However, the existing lodash contained legacy code and unnecessary defensive logic that didn't fit modern browser environments, and it had efficiency issues such as not supporting tree-shaking.

To solve this, the Toss team began developing es-toolkit, optimized for modern JavaScript environments, based on their internally used @toss/utils. The main goal was to remove lodash's inefficient logic to improve performance and reduce code size.

By actually implementing the core functions and measuring performance, they found that simply removing unnecessary logic achieved a 2x to over 10x speed improvement compared to the existing library. Based on this performance advantage, es-toolkit now records 20 million weekly downloads and has grown into a global project adopted by major libraries such as Yarn and Recharts.