Looking for JavaScript function to escape a string for JavaScript string

Question

I'm am looking for a JavaScript equivalent for this (Java) code: org.apache.commons.lang.StringEscapeUtils.escapeJavaScript(String)

So I can use it in JavaScript like:

loop ... foo = something;
  elem.setAttribute("onclick", "bar(event, 'this:" + used_here(foo) + "');");
  foo = something else;
repeat loop

So what is missing here is the function used_here(), which would properly escape its parameter according to JavaScript string rules.

Is there such a function that is standard (supported by major browsers) ?

--

Explanation for false duplicate: This is not about HTML escaping.

So NOT THIS: " -> "
But this:    " -> \"

Answer 1

Begging your pardon for any offense, but this is like asking how to implement an address book app for a rotary phone, or an anti-arrow armour for homing pigeons. :) In this day and age, you should almost never have the reason to have JavaScript as string in a HTML attribute.

elem.setAttribute("onclick", "alert('this:" + used_here(foo) + "');");

is these days very cleanly written as

let foo = `Chief O'Brien & Dwayne "The Rock" Johnson can now have any special chars they want!`;
let elem = document.querySelector('button');

elem.addEventListener('click', evt => {
  alert(foo);
});

<button>Click me!</button>

EDIT: the loop.

let elems = document.querySelectorAll('button');

elems.forEach((elem, i) => {
  let foo = `Button ${i + 1}`; // foo is different, but it is local
  elem.addEventListener('click', evt => {
    alert(foo);
  });
});

<button>Click me!</button>
<button>No, click me!</button>
<button>No, me!</button>

Or, to support IE8, with jQuery, intentionally not using .each, because I want to demonstrate old-school for loop where closure over foo has to be prevented:

var elems = $('button');

var i, elem, foo;
for (i = 0; i < elems.length; i++) {
  elem = elems[i];
  foo = "Button " + (i + 1);
  (function(foo) {
    $(elem).on('click', function(evt) {
      alert(foo);
    });
  })(foo);
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<button>Click me!</button>
<button>No, click me!</button>
<button>No, me!</button>

Answer 2

I converted over the escapeJavaStyleString from org.apache.commons.lang.StringEscapeUtils.escapeJavaScript into javascript:

function escapeJavaStyleString(str, escapeSingleQuote, escapeForwardSlash) {
    if (str == null) {
        return '';
    }
    const sz = str.length;
    let out = '';
    for (let i = 0; i < sz; i++) {
        const ch = str.charAt(i);
        // handle unicode
        if (ch > 0xfff) {
            out += "\\u" + ch.toString(16);
        } else if (ch > 0xff) {
            out += "\\u0" + ch.toString(16);
        } else if (ch > 0x7f) {
            out += "\\u00" + ch.toString(16);
        } else if (ch < 32) {
            switch (ch) {
                case '\b':
                    out += '\\';
                    out += 'b';
                    break;
                case '\n' :
                    out += '\\';
                    out += 'n';
                    break;
                case '\t' :
                    out += '\\';
                    out += 't';
                    break;
                case '\f' :
                    out += '\\';
                    out += 'f';
                    break;
                case '\r' :
                    out += '\\';
                    out += 'r';
                    break;
                default :
                    if (ch > 0xf) {
                        out += "\\u00" + ch.toString(16);
                    } else {
                        out += "\\u000" + ch.toString(16);
                    }
                    break;
            }
        } else {
            switch (ch) {
                case '\'' :
                    if (escapeSingleQuote) {
                        out += '\\';
                    }
                    out += '\'';
                    break;
                case '"' :
                    out += '\\';
                    out += '"';
                    break;
                case '\\' :
                    out += '\\';
                    out += '\\';
                    break;
                case '/' :
                    if (escapeForwardSlash) {
                        out += '\\';
                    }
                    out += '/';
                    break;
                default :
                    out += ch;
                    break;
            }
        }
    }
    
    return out;
}

console.log(escapeJavaStyleString('testing("bleh")'));