Printing emojis with JavaScript and HTML
Why does this work:
<p id="emoji">😄</p>
And this doesn't:
document.getElementById("emoji").innerHTML = String.fromCharCode(parseInt('1f604', 16));
Answer
A 'char' in JS terms is actually a UTF-16 code unit, not a full Unicode character. (This sad state of affairs stems from ancient times when there wasn't a difference*.) To use a character outside of the Basic Multilingual Plane you have to write it in the UTF-16-encoded form of a surrogate pair of two 16-bit code units:
String.fromCharCode(0xD83D, 0xDE04)
In ECMAScript 6 we will get some interfaces that let us deal with strings as if they were full Unicode code points, though they are incomplete and are only a façade over the String type which is still stored as a code unit sequence. Then we'll be able to do:
String.fromCodePoint(0x1F604)
See this question for some polyfill code to let you use this feature in today's browsers.
(*: When I get access to a time machine I'm leaving Hitler alone and going back to invent UTF-8 earlier. UTF-16 must never have been!)