specInJs.js

// this is a direct translation to code of the spec
if(!RegExp.escape){
RegExp.escape = (S) => {
  // 1. let str be ToString(S).
  // 2. ReturnIfAbrupt(str).
  let str = String(S);
  // 3. Let cpList be a List containing in order the code
  // points as defined in 6.1.4 of str, starting at the first element of str.
  let cpList = Array.from(str[Symbol.iterator]());
  // 4. let cuList be a new List
  let cuList = [];
  // 5. For each code point c in cpList in List order, do:
  for(let c of cpList){
    // i. If c is a SyntaxCharacter then do:
    if("^$\\.*+?()[]{}|".indexOf(c) !== -1){
      // a. Append "\" to cuList.
      cuList.push("\\");
    }
    // Append c to cpList.
    cuList.push(c);
  }
  //6. Let L be a String whose elements are, in order, the elements of cuList.
  let L = cuList.join("");
  // 7. Return L.
  return L;
};
}