A type-checking function in JavaScript

istype.js

window.istype = function(value, explicit = false) {
  let type = Object.prototype.toString.apply(value).match(
    /\[object ([A-Za-z_0-9]+)\]/
  )[1]

  switch (type) {
    case "Boolean":
    case "String":
    case "BigInt":
    case "Undefined":
    case "Null":
    case "Symbol":
    case "Array":
    case "Date":
    case "RegExp":
    case "Function":
    case "Error":
      break
    case "Number":
      if (!Number.isFinite(value)) type = Number.isNaN(value)
        ? "NaN"
        : "Infinity"
      break
    default:
      if (!explicit) type = "Object"
  }

  return type
}