prefer-rest-params

arguments looks like an array but isn't one. It has no map, slice or join. And function log(level) doesn't show that the function takes more than one argument. A rest parameter such as ...parts is a real array, and you can see it in the signature.

Reading a named property, such as arguments.length, isn't reported.

This rule is on by default in TypeScript files.

Configure

On by default as a warning. To turn it off:

[lint.rules]
"prefer-rest-params" = "off" # or "error"

Examples

Reported:

function log(level) {
  const parts = Array.prototype.slice.call(arguments, 1);
  console.log(level, parts.join(" "));
}

Not reported:

function log(level, ...parts) {
  console.log(level, parts.join(" "));
}

function hasOptions() {
  return arguments.length > 1;
}