Escape the required characters and surround with double quotes to produce a valid ECMAScript string literal from any normal string.

escape_as_javascript_string_literal.py

def escape_as_javascript_string_literal(text):
    """
    Escape the required characters and surround with double quotes to produce a 
    valid ECMAScript string literal from any normal string.

    ----

    ECMA-262 -> 7.8.4 String Literals

    A string literal is zero or more characters enclosed in single or
    double quotes. Each character may be represented by an escape
    sequence. All characters may appear literally in a string literal
    except for the closing quote character, backslash, carriage return,
    line separator, paragraph separator, and line feed. Any character may
    appear in the form of an escape sequence.

    ECMA-262 -> 7.3 Line Terminators

    \u000A Line Feed           <LF>  \n
    \u000D Carriage Return     <CR>  \r
    \u2028 Line separator      <LS>  
    \u2029 Paragraph separator <PS>

    Note: esacping the single quote is not required as we use double quotes.
    """

    new_text = "";
    for char in text:
        # closing quote character
        if char is '"':
          new_text += "\\" + "\""
        # backslash
        if char is '\\':
          new_text += "\\" + "\\"
        # carriage return,
        if char is '\r':
          new_text += "\\" + "r"
        # line separator, 
        if char is '\u2028':
          new_text += "\\" + "u2028"
        # paragraph separator, 
        if char is '\u2029':
          new_text += "\\" + "u2029"
        # line feed
        if char is '\n':
          new_text += "\\" + "n"
        # otherwise normal
        else:
          new_text += char
    return "\"" + new_text + "\""