How to remove only html tags in a string using javascript

Question

I want to remove html tags from given string using javascript. I looked into current approaches but there are some unsolved problems occured with them.

Current solutions

(1) Using javascript, creating virtual div tag and get the text

  function remove_tags(html)
  {
       var tmp = document.createElement("DIV");
       tmp.innerHTML = html; 
       return tmp.textContent||tmp.innerText; 
  }

(2) Using regex

  function remove_tags(html)
  {
       return html.replace(/<(?:.|\n)*?>/gm, '');
  }

(3) Using JQuery

  function remove_tags(html)
  {
       return jQuery(html).text();
  }

These three solutions are working correctly, but if the string is like this

  <div> hello <hi all !> </div>

stripped string is like hello . But I need only remove html tags only. like hello <hi all !>

Edited: Background is, I want to remove all the user input html tags for a particular text area. But I want to allow users to enter <hi all> kind of text. In current approach, its remove any content which include within <>.

Answer 1

Using a regex might not be a problem if you consider a different approach. For instance, looking for all tags, and then checking to see if the tag name matches a list of defined, valid HTML tag names:

var protos = document.body.constructor === window.HTMLBodyElement;
    validHTMLTags  =/^(?:a|abbr|acronym|address|applet|area|article|aside|audio|b|base|basefont|bdi|bdo|bgsound|big|blink|blockquote|body|br|button|canvas|caption|center|cite|code|col|colgroup|data|datalist|dd|del|details|dfn|dir|div|dl|dt|em|embed|fieldset|figcaption|figure|font|footer|form|frame|frameset|h1|h2|h3|h4|h5|h6|head|header|hgroup|hr|html|i|iframe|img|input|ins|isindex|kbd|keygen|label|legend|li|link|listing|main|map|mark|marquee|menu|menuitem|meta|meter|nav|nobr|noframes|noscript|object|ol|optgroup|option|output|p|param|plaintext|pre|progress|q|rp|rt|ruby|s|samp|script|section|select|small|source|spacer|span|strike|strong|style|sub|summary|sup|table|tbody|td|textarea|tfoot|th|thead|time|title|tr|track|tt|u|ul|var|video|wbr|xmp)$/i;

function sanitize(txt) {
    var // This regex normalises anything between quotes
        normaliseQuotes = /=(["'])(?=[^\1]*[<>])[^\1]*\1/g,
        normaliseFn = function ($0, q, sym) { 
            return $0.replace(/</g, '&lt;').replace(/>/g, '&gt;'); 
        },
        replaceInvalid = function ($0, tag, off, txt) {
            var 
                // Is it a valid tag?
                invalidTag = protos && 
                    document.createElement(tag) instanceof HTMLUnknownElement
                    || !validHTMLTags.test(tag),

                // Is the tag complete?
                isComplete = txt.slice(off+1).search(/^[^<]+>/) > -1;

            return invalidTag || !isComplete ? '&lt;' + tag : $0;
        };

    txt = txt.replace(normaliseQuotes, normaliseFn)
             .replace(/<(\w+)/g, replaceInvalid);

    var tmp = document.createElement("DIV");
    tmp.innerHTML = txt;

    return "textContent" in tmp ? tmp.textContent : tmp.innerHTML;
}

Working Demo: http://jsfiddle.net/m9vZg/3/

This works because browsers parse '>' as text if it isn't part of a matching '<' opening tag. It doesn't suffer the same problems as trying to parse HTML tags using a regular expression, because you're only looking for the opening delimiter and the tag name, everything else is irrelevant.

It's also future proof: the WebIDL specification tells vendors how to implement prototypes for HTML elements, so we try and create a HTML element from the current matching tag. If the element is an instance of HTMLUnknownElement, we know that it's not a valid HTML tag. The validHTMLTags regular expression defines a list of HTML tags for older browsers, such as IE 6 and 7, that do not implement these prototypes.