rxjs/src/internal/util/isNumeric.ts

Reactive Extensions for modern JavaScript

export function isNumeric(val: any): val is number | string {
  // parseFloat NaNs numeric-cast false positives (null|true|false|"")
  // ...but misinterprets leading-number strings, particularly hex literals ("0x...")
  // subtraction forces infinities to NaN
  // adding 1 corrects loss of precision from parseFloat (#15100)
  return !Array.isArray(val) && (val - parseFloat(val) + 1) >= 0;
}