avoid stack overflow

trampoline.js

const trampoline = fn => (...args)=>{
  let result = fn(...args)
  while (typeof result === 'function')
    result = result()
  return result
}
const sum = (number,step=0)=>(
  !number?step:()=>sum(number-1,step+number)
)
// const tsum = trampoline(sum)(500000) // currying
const tsum = trampoline(sum)
const result = tsum(50000)
console.log(result)