Return '@ null' if args is null ASAP

[matamatanot]

If args[i] is null, always return @null.

Now, check typeof args[i] === 'string' and run String(args[i]). This is unnecessary.
This fix improve readability and performance.

[matamatanot]

I have committed into vercel:master. Was vercel:next more appropriate?
I'm skipping the error on ts-ignore using --no-verify. It seems to have already been fixed in vercel:next.

/swr/src/use-swr.ts
27:1 error Do not use "// @ts-ignore" comments because they suppress compilation errors

[shuding]

@matamatanot yeah if it’s not a breaking change please target master. next is for 1.0 👍

[matamatanot]

There is an error. The cause is #754.

[shuding]

So this changes the hook behavior:

Before:

useSWR([1, 2, null, 3, 4]) // => key will be `arg@1@2@null@3@4`

Now:

useSWR([1, 2, null, 3, 4]) // => key will be `arg@1@2@null`

I think that feels inconsistent and may also cause key conflicts. But it is indeed a good question: should we skip the request if one of the args is null...?

[matamatanot]

@shuding
I mistook for for forEach. Is it from a performance perspective that used for?

[matamatanot]

This is an example of using reduce. It's not clear if it improved readability and performance. Instead, it may be worse.

function hash2(args: any[]): string {
  if (!args.length) return ''
  return args.reduce((acc: string, current: any) => {
    if (current === null) {
      return (acc += '@null')
    } else if (typeof current !== 'object' && typeof current !== 'function') {
      if (typeof current === 'string') {
        return (acc += '@' + '"' + current + '"')
      } else {
        return (acc += '@' + String(current))
      }
    } else {
      if (!table.has(current)) {
        table.set(current, counter++)
        return (acc += '@' + (counter - 1))
      } else {
        return (acc += '@' + table.get(current))
      }
    }
  }, 'arg')
}

[shuding]

Yeah I think as a small util, it's better to use for due to performance.

[matamatanot]

Using the continue statement. If you don't find it useful, you can close this.

[shuding]

Thanks!