How do you safely wrap a JS string variable in double quotes?

Question

Obviously, when you create the actual string literal yourself, you will escape the backslash double quote character.

var foo = "baz\"bat";

As with a few other control characters, such as line breaks and backslashes.

var bar = "baz\\bat\nmynew line and a \"quote\" ";

but if you just wrap an existing variable in a quote symbol, that is, you give it to some other system that requires an input quote, there is some confusion.

Obviously, you need to avoid any potential double quotes that are in the string.

var doubleQuoteRe = /\"/g;
var quoted = "\"" + unquoted.replace(escaper, '\\\"') + "\"";

, , . , , . , .

Answer 1

, , -

String.prototype.inquotes=function(){
 return '"'+this.replace(/(^|[^\\])"/g,'$1\\"')+'"';
}

Answer 2

FF

str.quote()

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/quote polyfill

    if(!String.prototype.quote){
  // oop version - no dependencies
  String.prototype.quote = (function(){
    // prepare fallback
    // ----------------
    // backslash escape double quotes and backslashes
    var escp_regex = /[\\"]/g,
      escp_callback = '\\$&',
      // escape control characters
      ctrl_map = {
        '\b': '\\b', // backspace
        '\t': '\\t', // tab
        '\n': '\\n', // new line
        '\f': '\\f', // form feed
        '\r': '\\r'  // carriage return
      },
      // don't rely on `Object.keys(ctrl_map).join('')`
      ctrl_regex = new RegExp('[\b\t\n\f\r]', 'g'),
      ctrl_callback = function(match){
        return ctrl_map[match];
      },
      // hex-escape, spare out control characters and ASCII printables
      // [0-7,11,14-31,127-255]
      xhex_regex = /[\x00-\x07\x0B\x0E-\x1F\x7F-\xFF]/g,
      xhex_callback = function(match, char_code){
        char_code = match.charCodeAt(0);
        return '\\x' + (char_code < 16 ? '0' : '') + char_code;
      },
      // hex-escape all others
      uhex_regex = /[\u0100-\uFFFF]/g,
      uhex_callback = function(match, char_code){
        char_code = match.charCodeAt(0);
        return '\\u' + (char_code < 4096 ? '0' : '') + char_code;
      },
      // delegate to native `JSON.stringify` if available
      stringify = typeof JSON !== 'undefined' && JSON.stringify;

    // return actual polyfill
    // ----------------------
    return function(){
      var self = this; // promote compression
      if(self == null) throw new TypeError('can\'t convert ' + self + ' to object');
      if(stringify) return stringify(self);
      return '"' + self
        .replace(escp_regex, escp_callback)
        .replace(ctrl_regex, ctrl_callback)
        .replace(xhex_regex, xhex_callback)
        .replace(uhex_regex, uhex_callback) + '"';
    }
  }());

  // generic version - requires Function#bind
  String.quote = Function.call.bind(''.quote);
}

Answer 3

, , , ( !) / , ASCII. Crockford quote(), mercurial.intuxication.org.

Answer 4

: , :

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, 1 , , 5- :

foo\"   

(foo) , .

( , , "foo \" ")

, ,

foo\\"     

. , , .

"foo\\""

on the other hand, if I do the first step 1 - replacing all backslashes with double backslashes gives

foo\\"

and then step 2 - replacing the quote with a slash gives

foo\\\"

Now that I am completing my meaning in quote symbols, I finally get

"foo\\\""

what is right.