JS Newbie JS Newbie - 6 months ago 26
HTML Question

JavaScript Unicode's length (astral symbols)

I have a

< input type="text" >
(in HTML) and everytime I add a character I do a
if text.length < x {...}
(in JavaScript).

The problem is that the Unicode special characters/astral symbols (\u{.....}, the ones with more than 4 hex/ non-BMP characters) "are stored as two code units and so the length property will return 2 instead of 1."

(https://mixmax.com/blog/unicode-woes-in-javascript)

I wanna be able to get 1 for all symbols or 2, as long as it doesn't mix some with 1 and some with 2 because I have to have a working limit on the size of the visual text.

I think the solutions is here: https://mathiasbynens.be/notes/javascript-unicode#accounting-for-astral-symbols but I'm not sure how to use that.

My if is something like this:

if(document.getElementById("1").value.length<16){


Edit (it's working!):

<html>
<head>
<style>
input{background:white;border:1px solid;height:30;outline-color:black;position:absolute;top:389;width:30}
</style>
<script>
<!--
function Add(symbol){
if (countSymbols(document.getElementById("1").value)<16) {
document.getElementById("1").value+=symbol}
if(document.getElementById("1").value.length==16 && document.getElementById("1").value=="\u{1F4BB}\u{1F3AE}\u{1F3C3}\u{1F525}\u2764\u{1D7CF}\u{1D7D1}\u{1F4B0}\u2757"){
document.getElementById("1").style.background="#00BB00"}
if(document.getElementById("1").value.length==16 && document.getElementById("1").value!="\u{1F4BB}\u{1F3AE}\u{1F3C3}\u{1F525}\u2764\u{1D7CF}\u{1D7D1}\u{1F4B0}\u2757"){
document.getElementById("1").style.background="#BB0000"}
}
function countSymbols(string) {
var regexAstralSymbols = /[\uD800-\uDBFF][\uDC00-\uDFFF]/g;
return string
// Replace every surrogate pair with a BMP symbol.
.replace(regexAstralSymbols, '_')
// …and *then* get the length.
.length;
}
//-->
</script>
</head>
<body>
<input readOnly="true" id="1" style="left:573;outline:0;padding:5 8;top:356;width:294">
<input onclick="Add('\u{1F4BB}')" style="left:573" type="button" value="&#128187">
<input onclick="Add('\u{1F3AE}')" style="left:606" type="button" value="&#127918">
<input onclick="Add('\u{1F3C3}')" style="left:639" type="button" value="&#127939">
<input onclick="Add('\u{1F525}')" style="left:672" type="button" value="&#128293">
<input onclick="Add('\u2764')" style="left:705" type="button" value="&#10084">
<input onclick="Add('\u{1D7CF}')" style="left:738" type="button" value="&#120783">
<input onclick="Add('\u{1D7D1}')" style="left:771" type="button" value="&#120785">
<input onclick="Add('\u{1F4B0}')" style="left:804" type="button" value="&#128176">
<input onclick="Add('\u2757')" style="left:837" type="button" value="&#10071">
</body>
</html>

Answer

I think you have most of the research done, you only need to put all of it together:

Taking the function that your link provides:

function countSymbols(string) {
    var regexAstralSymbols = /[\uD800-\uDBFF][\uDC00-\uDFFF]/g;
    return string
        // Replace every surrogate pair with a BMP symbol.
        .replace(regexAstralSymbols, '_')
        // …and *then* get the length.
        .length;
}

your if should be

if (countSymbols(document.getElementById("1").value)<16) { ...}

For example: countSymbols('