转义RegExp字符串中特殊的字符"^", "$", "\", ".", "*", "+", "?", "(", ")", "[", "]", "{", "}", "|"

/**
 * 转义RegExp字符串中特殊的字符"^", "$", "\", ".", "*", "+", "?", "(", ")", "[", "]", "{", "}", "|"
 * Escapes the `RegExp` special characters "^", "$", "\", ".", "*", "+",
 * "?", "(", ")", "[", "]", "{", "}", and "|" in `string`.
 * @param {string} [string=''] The string to escape
 * @returns {string} Returns the escaped string
 * @example
 * escapeRegExp('[lodash](https://lodash.com/)')
 * // => '\[lodash\]\(https://lodash\.com/\)'
 */

import toString from "./toString"

// Used to match `RegExp`
var reRegExpChar = /[\\^$.*+?()[\]{}|]/g
var reHasRegExpChar = new RegExp(reRegExpChar.source)

function escapeRegExp(string) {
  string = toString(string)
  return string && reHasRegExpChar.test(string)
    ? string.replace(reRegExpChar, "\\$&")
    : string
}

export default escapeRegExp

/**
 * Converts `value` to a string. An empty string is returned for `null` and `undefined` values.
 * The sign of `-0` is preserved.
 * 转换`value`成字符串，`null`和`undefined`返回空字符串，`-0`转成'-0'
 * @param {*} value The value to convert
 * @retuens {string} Returns the converted string
 * @example
 * toString(null)
 * // => ''
 * toString(-0)
 * // => '-0'
 * toString([1, 2, 3])
 * // => '1, 2, 3'
 * toString({a: 1})
 * // => [object Object]
 */
 
const symbolTag = "[object Symbol]"
 
function isObjectLike(value) {
  return typeof value == "object" && value !== null;
}
 
function isSymbol(value) {
  return (
    typeof value === "symbol" ||
    (isObjectLike(value) && Object.prototype.toString.call(value) === symbolTag)
  )
}
 
function arrayMap(array, iteratee) {
  var index = -1,
    length = array == null ? 0 : array.length,
    result = Array(length)
 
  while (++index < length) {
    result[index] = iteratee(array[index], index, array)
  }
  return result
}
 
function baseToString(value) {
  if (typeof value === "string") {
    return value
  }
  if (Array.isArray(value)) {
    return arrayMap(value, baseToString) + ""
  }
  if (isSymbol(value)) {
    return Symbol.prototype.toString
      ? Symbol.prototype.toString.call(value)
      : ""
  }
  var result = value + ""
  return result == "0" && 1 / value == -Infinity ? "-0" : result
}
 
function toString(value) {
  return value == null ? "" : baseToString(value)
}
 
export default toString