JavaScript Get real length of a string (without entities)

Question

I need to determine the length of string which may contain html-entities.

For example "&darr ;" (↓) would return length 6, which is correct, but I want these entities to be counted as only 1 character.

Answer 1

<div id="foo">&darr;</div>

alert(document.getElementById("foo").innerHTML.length); // alerts 1

So based on that rationale, create a div, append your mixed up entity ridden string to it, extract the HTML and check the length.

var div = document.createElement("div");
div.innerHTML = "↓↓↓↓";
alert(div.innerHTML.length); // alerts 4

Try it here.

You might want to put that in a function for convenience, e.g.:

function realLength(str) { // maybe there's a better name?
    var el = document.createElement("div");
    el.innerHTML = str;
    return el.innerHTML.length;   
}

Answer 2

Since there's no solution using jQuery yet:

var str = 'lol&';
alert($('<span />').html(str).text().length); // alerts 4

Uses the same approach like karim79, but it never adds the created element to the document.

Answer 3

You could for most purposes assume that an ampersand followed by letters, or a possible '#' and numbers, followed by a semicolon, is one character.

var strlen=string.replace(/&#?[a-zA-Z0-9]+;/g,' ').length;

Answer 4

If you are running the javascript in a browser I would suggest using it to help you. You can create an element and set its innerHTML to be your string containing HTML-entities. Then extract the contents of that element you just created as text.

Here is an example (uses Mootools): http://jsfiddle.net/mqchen/H73EV/

Answer 5

Unfortunately, JavaScript does not natively support encoding or decoding of HTML entities, which is what you will need to do to get the 'real' string length. I was able to find this third-party library which is able to decode and encode HTML entities and it appears to work well enough, but there's no guaranteeing how complete it will be.

http://www.strictly-software.com/htmlencode

Answer 6

Using ES6 (introduces codePointAt():

function strlen (str) {
    let sl = str.length
    let chars = sl
    for (i = 0; i < sl; i++) if (str.codePointAt(i) > 65535) {
       chars--;
       i++;
    }
    return chars
}

Beware charCodeAt() does not work the same way.