A long parameter list can indicate that a new structure should be created to wrap the numerous parameters or that the function is doing too many things.
With a maximum number of 4 parameters:
function doSomething(param1: number, param2: number, param3: number, param4: number, param5: number) {
...
}
function doSomething(param1: number, param2: number, param3: number, param4: number) {
...
}