1. Lookbehind in JS regular expressions

    The positive lookbehind (`(?<= )`) and negative lookbehind (`(?<! )`) zero-width assertions in JavaScript regular expressions can be used to ensure a pattern is preceded by another pattern.

  2. csscounterstylerule api: negative

  3. htmltablerowelement api: insertcell: `index` parameter can be `-1`

  4. css at-rule: `@counter-style`: negative

  5. css property: z-index: negative values

  6. javascript built-in: intl: numberformat: `numberformat()` constructor: `options` parameter: `options.signdisplay` parameter: `negative` value

  7. javascript built-in: number: negative_infinity

  8. lookahead assertions in js regular expressions