[{"id":"a2a14b73-a655-4913-9a73-43e6da929aa3","thread_id":"43fe3cd4-4ca0-4dee-9b5c-ff122d8b8fa8","created_at":"2025-11-26T16:07:22Z","state":"done","prompt":"Will js rountrip strings cleanly even if they are arbitrary bytes?","reply":"<details><summary>Searched with Kagi<p></p>\n<ul>\n<li>javascript string arbitrary bytes roundtrip</li>\n<li>javascript string encoding non-utf8</li>\n<li>javascript byte array to string and back</li></ul></summary><br>\nSources (30):<br>\n<strong>Reading bytes from a JavaScript string</strong><br>\n<a href=\"https://stackoverflow.com/questions/1240408/reading-bytes-from-a-javascript-string\" target=\"_blank\">https://stackoverflow.com/questions/1240408/reading-bytes-from-a-javascript-string</a><br>\nNov 26, 2009 Use bit operations to extract bytes from a JavaScript string. For example, `stringToBytes` function can be used to get bytes from a string.\n\n<p><strong>how do I add an arbitrary byte value onto the end of a string? (JavaScript)</strong><br>\n<a href=\"https://stackoverflow.com/questions/5913930/how-do-i-add-an-arbitrary-byte-value-onto-the-end-of-a-string-javascript\" target=\"_blank\">https://stackoverflow.com/questions/5913930/how-do-i-add-an-arbitrary-byte-value-onto-the-end-of-a-string-javascript</a><br>\nJun 29, 2017 4 in JavaScript, how do I add an arbitrary byte value onto the end of a string? I'm trying to construct an array which contains both ASCII and binary data, for passing to a remote server.</p>\n<p><strong>How can I encode arbitrary bytes/data to base64... - Stack Overflow</strong><br>\n<a href=\"https://stackoverflow.com/questions/5757849/how-can-i-encode-arbitrary-bytes-data-to-base64-format-using-javascript\" target=\"_blank\">https://stackoverflow.com/questions/5757849/how-can-i-encode-arbitrary-bytes-data-to-base64-format-using-javascript</a><br>\nJun 22, 2017 Learn more about Teams. How can I encode arbitrary bytes/data to base64 format using Javascript?7. For example, say I wanted to encode a 64-bit signed integer into base64, how could I (if possible) do it in Javascript? To clarify, I want to encode the actual bits/bytes of data, NOT the string or string representation of the data.</p>\n<p><strong>Javascript integer to binary string round trip loses bits</strong><br>\n<a href=\"https://stackoverflow.com/questions/41685832/javascript-integer-to-binary-string-round-trip-loses-bits\" target=\"_blank\">https://stackoverflow.com/questions/41685832/javascript-integer-to-binary-string-round-trip-loses-bits</a><br>\n I'm trying to convert a binary string to an integer and back again in javascript (Mostly so I can move my binary arrays across a network and more efficiently). Only I'm having a problem. It appears that while converting a 64-bit array back and forth, I lose some of the bits. My conversion functions looks like this:</p>\n<p><strong>Converting byte array to string in javascript - Stack Overflow</strong><br>\n<a href=\"https://stackoverflow.com/questions/3195865/converting-byte-array-to-string-in-javascript\" target=\"_blank\">https://stackoverflow.com/questions/3195865/converting-byte-array-to-string-in-javascript</a><br>\n How do I convert a byte array into a string? I have found these functions that do the reverse: function string2Bin(s) { var b = new Array(); var last = s.length; for (var i = 0; i ...</p>\n<p><strong>Is it safe to decode an arbitrary UTF8-byte-chunk to string?</strong><br>\n<a href=\"https://stackoverflow.com/questions/63069231/is-it-safe-to-decode-an-arbitrary-utf8-byte-chunk-to-string\" target=\"_blank\">https://stackoverflow.com/questions/63069231/is-it-safe-to-decode-an-arbitrary-utf8-byte-chunk-to-string</a><br>\n Is it safe to decode an UTF8-string that has been hacked into arbitrary byte-chunks to string (chunk-wise)? Also, what about an arbitrary encoding ? Context is this method: async getFileAsync(fileN...</p>\n<p><strong>javascript - How to split a string into chunks of a particular byte ...</strong><br>\n<a href=\"https://stackoverflow.com/questions/57068850/how-to-split-a-string-into-chunks-of-a-particular-byte-size\" target=\"_blank\">https://stackoverflow.com/questions/57068850/how-to-split-a-string-into-chunks-of-a-particular-byte-size</a><br>\n Is there a way to split a string into strings of a particular byte length? I could either: assume that strings will only contain 1 byte per character allow for the 'worst case scenario' that each character is 4 bytes but would prefer a more accurate solution. I would be interested to know of both Node and plain JavaScript solutions, if they ...</p>\n<p><strong>Window: btoa () method - Web APIs | MDN - MDN Web Docs</strong><br>\n<a href=\"https://developer.mozilla.org/en-US/docs/Web/API/Window/btoa\" target=\"_blank\">https://developer.mozilla.org/en-US/docs/Web/API/Window/btoa</a><br>\n The btoa() method of the Window interface creates a Base64-encoded ASCII string from a binary string (i.e., a string in which each character in the string is treated as a byte of binary data).</p>\n<p><strong>Numbers and strings - JavaScript - MDN Web Docs - Mozilla</strong><br>\n<a href=\"https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Numbers_and_strings\" target=\"_blank\">https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/Numbers_and_strings</a><br>\nAug 26, 2025 This chapter introduces the two most fundamental data types in JavaScript: numbers and strings. We will introduce their underlying representations.</p>\n<p><strong>How many bytes in a JavaScript string? - Stack Overflow</strong><br>\n<a href=\"https://stackoverflow.com/questions/2219526/how-many-bytes-in-a-javascript-string\" target=\"_blank\">https://stackoverflow.com/questions/2219526/how-many-bytes-in-a-javascript-string</a><br>\n I have a javascript string which is about 500K when being sent from the server in UTF-8. How can I tell its size in JavaScript? I know that JavaScript uses UCS-2, so does that mean 2 bytes per character. However, does it depend on the JavaScript implementation? Or on the page encoding or maybe content-type?</p>\n<p><strong>UTF-8 - Wikipedia</strong><br>\n<a href=\"https://en.wikipedia.org/wiki/UTF-8\" target=\"_blank\">https://en.wikipedia.org/wiki/UTF-8</a><br>\n UTF-8 is a character encoding standard used for electronic communication. Defined by the Unicode Standard, the name is derived from Unicode Transformation Format – 8-bit. [1] As of July 2025, almost every webpage is transmitted as UTF-8. [2] UTF-8 supports all 1,112,064 [3] valid Unicode code points using a variable-width encoding of one to four one- byte (8-bit) code units. Code points with ...</p>\n<p><strong>How to remove invalid UTF-8 characters from a JavaScript ...</strong><br>\n<a href=\"https://stackoverflow.com/questions/2670037/how-to-remove-invalid-utf-8-characters-from-a-javascript-string\" target=\"_blank\">https://stackoverflow.com/questions/2670037/how-to-remove-invalid-utf-8-characters-from-a-javascript-string</a><br>\nNov 26, 2010 You can, if you need to for some reason, create a string holding characters used as placeholders for bytes. ie. using the character U+0080 ('\\ ...See more</p>\n<p><strong>How to parse non-UTF8 XML in browsers with Javascript?</strong><br>\n<a href=\"https://stackoverflow.com/questions/38292228/how-to-parse-non-utf8-xml-in-browsers-with-javascript\" target=\"_blank\">https://stackoverflow.com/questions/38292228/how-to-parse-non-utf8-xml-in-browsers-with-javascript</a><br>\nJun 22, 2017 *One way of understanding why: atob doesn't take the encoding of the original string as a parameter, so while it must internally decode base64 encoded data to bytes, it has to make an assumption on what character encoding those bytes are to then give you a Javascript string of characters, which I believe is internally encoded as UTF-16.</p>\n<p><strong>node.js - Nodejs convert string into UTF-8 - Stack Overflow</strong><br>\n<a href=\"https://stackoverflow.com/questions/20174280/nodejs-convert-string-into-utf-8\" target=\"_blank\">https://stackoverflow.com/questions/20174280/nodejs-convert-string-into-utf-8</a><br>\nAug 05, 2014 Buffer.from('someString', '<input-encoding>').toString('utf-8') This avoids any unnecessary dependencies that other answers require, since Buffer is included with node.js, and is already defined in the global scope.</p>\n<p><strong>JavaScript encoding with Special characters - Stack</strong><br>\n<a href=\"https://stackoverflow.com/questions/13248280/javascript-encoding-with-special-characters\" target=\"_blank\">https://stackoverflow.com/questions/13248280/javascript-encoding-with-special-characters</a><br>\nJun 25, 2024 ... sequences in this table and the ones php s json_encode ... Making statements based on opinion; back them up with references or personal experience.</p>\n<p><strong>jquery - Change JavaScript string encoding - Stack Overflow</strong><br>\n<a href=\"https://stackoverflow.com/questions/18879860/change-javascript-string-encoding\" target=\"_blank\">https://stackoverflow.com/questions/18879860/change-javascript-string-encoding</a><br>\nSep 21, 2013 Downloadify only accepts normal JavaScript strings or base64 encoded strings. Because of this, I've decided to compress my string using JSZip which generates a nicely base64 encoded string that can be passed to downloadify, and downloaded to my desktop. Huzzah! The issue is that the string I compressed, of course, is still the wrong encoding.This is what I found after a more specific Google search than just UTF-8 encode/decode. so for those who are looking for a converting library to convert between encodings, here you go. github.com/inexorabletash/text-encoding.</p>\n<p><strong>utf 8 - Javascript encoding checker ASCII/UFT8 -</strong><br>\n<a href=\"https://stackoverflow.com/questions/51447116/javascript-encoding-checker-ascii-uft8\" target=\"_blank\">https://stackoverflow.com/questions/51447116/javascript-encoding-checker-ascii-uft8</a><br>\nOct 13, 2025 ... to replicate mb_detect_encoding from PHP with javascript ... Making statements based on opinion; back them up with references or personal experience.</p>\n<p><strong>Using encodeURI() vs. escape() for utf-8 strings in JavaScript</strong><br>\n<a href=\"https://stackoverflow.com/questions/25003217/using-encodeuri-vs-escape-for-utf-8-strings-in-javascript\" target=\"_blank\">https://stackoverflow.com/questions/25003217/using-encodeuri-vs-escape-for-utf-8-strings-in-javascript</a><br>\n From your question I assume you have a JavaScript string and you want to convert encoding to UTF-8 and finally store the string in some escaped form. First of all it's important to note that JavaScript strings enconding is UCS-2, similar to UTF-16, different from UTF-8.</p>\n<p><strong>html - Change charset of javascript generated</strong><br>\n<a href=\"https://stackoverflow.com/questions/36195771/change-charset-of-javascript-generated-document-to-utf8\" target=\"_blank\">https://stackoverflow.com/questions/36195771/change-charset-of-javascript-generated-document-to-utf8</a><br>\nOct 12, 2025 I found out that the problem only exists when I used ... Making statements based on opinion; back them up with references or personal experience.</p>\n<p><strong>javascript - Remove non-ascii character in string - Stack Overflow</strong><br>\n<a href=\"https://stackoverflow.com/questions/20856197/remove-non-ascii-character-in-string\" target=\"_blank\">https://stackoverflow.com/questions/20856197/remove-non-ascii-character-in-string</a><br>\n Note that although the encoding of the embedded character is UTF-8, the encoding in the regular expression is not. Although the character is embedded in the string as three bytes (in my case) of UTF-8, the instructions in the regular expression must use the two-byte Unicode.</p>\n<p><strong>Converting byte array to string in javascript</strong><br>\n<a href=\"https://stackoverflow.com/questions/3195865/converting-byte-array-to-string-in-javascript\" target=\"_blank\">https://stackoverflow.com/questions/3195865/converting-byte-array-to-string-in-javascript</a><br>\nNov 26, 2010 Do you want to convert a byte array to a string, or an array of bits to a string?</p>\n<p><strong>Get byte array of string in .NET and convert back in Javascript</strong><br>\n<a href=\"https://stackoverflow.com/questions/22535917/get-byte-array-of-string-in-net-and-convert-back-in-javascript\" target=\"_blank\">https://stackoverflow.com/questions/22535917/get-byte-array-of-string-in-net-and-convert-back-in-javascript</a><br>\nJun 22, 2017 Then the next environment is Javascript, and I'm attempting to convert the byte array back to a string format: var str = unescape(encodeURIComponent(\"Hello\")); var arr = []So once I had my byte array, placed that into a string and sent the data to my second application. In javascript, I would get substrings of the original byte array string, and in pieces get the matching ASCII character using String.fromCharCode().</p>\n<p><strong>javascript - Converting byte array to string - Stack Overflow</strong><br>\n<a href=\"https://stackoverflow.com/questions/21896447/converting-byte-array-to-string\" target=\"_blank\">https://stackoverflow.com/questions/21896447/converting-byte-array-to-string</a><br>\nJun 20, 2017 I am using ssh2 to execute ls -1 command on remote computer and get response like byte array. I convert to string with function function ab2str(buf) { return String.fromCharCode.apply(null, new Uint16Array(buf)); } but when I try to split resulted/converted string by newline it doesn't work. (I have tried and asked on stackoverflow how to split and tried all solutions but it doesn't work ...</p>\n<p><strong>JavaScript - Convert Byte Array to String</strong><br>\n<a href=\"https://www.geeksforgeeks.org/javascript/how-to-convert-byte-array-to-string-in-javascript/\" target=\"_blank\">https://www.geeksforgeeks.org/javascript/how-to-convert-byte-array-to-string-in-javascript/</a><br>\nJul 23, 2025 The TextDecoder API is a modern and efficient way to convert a byte array (Uint8Array) to a string. It's supported in both browsers and Node.js.</p>\n<p><strong>JavaScript Program to Convert Byte Array to JSON - GeeksforGeeks</strong><br>\n<a href=\"https://www.geeksforgeeks.org/javascript/javascript-program-to-convert-byte-array-to-json/\" target=\"_blank\">https://www.geeksforgeeks.org/javascript/javascript-program-to-convert-byte-array-to-json/</a><br>\nAug 31, 2023 Converting a byte array to JSON means transforming a sequence of bytes into a structured JSON format, often involving decoding bytes to a text string and then parsing it into JSON data.This effectively transforms the byte array into a JSON format. Example: JavaScript. function byteArrayToJson(byteArray) { let jsonString = Array.from(byteArray).map(byte => String.fromCharCode(byte)).join(''); return JSON.parse(jsonString)</p>\n<p><strong>JavaScript Convert bytes to human-readable string - GeeksforGeeks</strong><br>\n<a href=\"https://www.geeksforgeeks.org/javascript/javascript-convert-bytes-to-human-readable-string/\" target=\"_blank\">https://www.geeksforgeeks.org/javascript/javascript-convert-bytes-to-human-readable-string/</a><br>\nJun 07, 2019 Given the size of a file (in Bytes), the task is to convert it into human-readable form using JavaScript. Here are a few methods to discuss.Example 2: This example converts the file Size(in Bytes) into human-readable form. It shows the values in decimal and for less than 1024 Bytes, it remains in Bytes. But, with a different approach. JavaScript.</p>\n<p><strong>Array.prototype.toString() - JavaScript - MDN Web Docs</strong><br>\n<a href=\"https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/toString\" target=\"_blank\">https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/toString</a><br>\nJul 20, 2025 The toString() method of Array instances returns a string representing the specified array and its elements.</p>\n<p><strong>JavaScript - Convert Byte Array to String - GeeksforGeeks</strong><br>\n<a href=\"https://www.geeksforgeeks.org/how-to-convert-byte-array-to-string-in-javascript/?itm_source=auth&itm_medium=contributions&itm_campaign=improvements\" target=\"_blank\">https://www.geeksforgeeks.org/how-to-convert-byte-array-to-string-in-javascript/?itm_source=auth&itm_medium=contributions&itm_campaign=improvements</a></p>\n<ol start=\"3\">\n<li>Using String.fromCharCode () Method This method uses String.fromCharCode to convert each byte in the array into a character.</li>\n</ol>\n<p>**How to convert strings to byte<a href=\"https://www.qvera.com/kb/index.php/402/how-to-convert-strings-to-byte-and-back-again\" target=\"_blank\">https://www.qvera.com/kb/index.php/402/how-to-convert-strings-to-byte-and-back-again</a>byte-and-back-again)<br>\nMar 05, 2014 This method is only available on Java strings. Not JavaScript strings. var bytes = example.getBytes(); qie.debug(\"Output plain text: \" + example);</p>\n<p><strong>JavaScript Program to Convert an Array into a String</strong><br>\n<a href=\"https://www.geeksforgeeks.org/javascript/javascript-program-to-convert-an-array-into-a-string/\" target=\"_blank\">https://www.geeksforgeeks.org/javascript/javascript-program-to-convert-an-array-into-a-string/</a><br>\n In this approach, we utilize template literals and the forEach () method to convert the array into a string. Template literals provide an easy way to concatenate strings, and forEach () allows us to iterate over each element of the array.</p>\n</details><p><strong>No</strong>, JavaScript strings do <strong>not</strong> cleanly round-trip arbitrary bytes. JavaScript strings are internally encoded as UTF-16, so treating them as raw byte containers risks data loss—especially for byte sequences that don’t map to valid Unicode.</p>\n<p>To move binary data through strings without corruption, use an explicit encoding:</p>\n<ul>\n<li><strong>Base64</strong> (<code>btoa</code> / <code>atob</code>) – simple and portable, but increases size by ~33 %.</li>\n<li><strong>TextEncoder / TextDecoder</strong> – convert between strings and <code>Uint8Array</code> with a chosen charset (usually UTF-8); this is the modern, lossless way.</li>\n<li><strong>Custom byte packing</strong> – possible with <code>String.fromCharCode</code>/<code>charCodeAt</code>, yet fragile and not recommended for general use.</li>\n</ul>\n<p>In short, <strong>never store raw bytes directly in a JavaScript string</strong>; always encode them first.</p>","md":"**No**, JavaScript strings do **not** cleanly round-trip arbitrary bytes. JavaScript strings are internally encoded as UTF-16, so treating them as raw byte containers risks data loss—especially for byte sequences that don’t map to valid Unicode.\n\nTo move binary data through strings without corruption, use an explicit encoding:\n\n- **Base64** (`btoa` / `atob`) – simple and portable, but increases size by ~33 %. \n- **TextEncoder / TextDecoder** – convert between strings and `Uint8Array` with a chosen charset (usually UTF-8); this is the modern, lossless way. \n- **Custom byte packing** – possible with `String.fromCharCode`/`charCodeAt`, yet fragile and not recommended for general use.\n\nIn short, **never store raw bytes directly in a JavaScript string**; always encode them first.","profile":{"id":null,"name":null,"model":"kimi-k2","model_name":"Kimi K2","model_provider":"moonshot","model_input_limit":1000000,"recommended":true,"model_info":"\n\n<div class=\"heading\">\n <div class=\"left\">\n \n \n \n <svg class=\"model-icon icon-xs\" data-model=\"kimi-k2\">\n <use href=\"#icon-moonshot\"/>\n </svg>\n <h3>\n \n <span class=\"model-provider\">Moonshot AI</span>\n \n <span class=\"model-name\">none</span>\n </h3>\n </div>\n\n \n <a href=\"/settings?p=custom_assistant&id=none\">\n <svg class=\"icon-sm edit-icon\" aria-hidden=\"true\">\n <use href=\"#icon-pencil\" />\n </svg>\n </a>\n \n</div>\n\n\n<hr />\n<ul>\n \n <li>\n <h4>\n Cost\n </h4>\n <span>\n \n \n \n\n \n \n \n\n <div class=\"score\" aria-label=\"Moderate\">\n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-cost --medium\"></div>\n \n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-cost --medium\"></div>\n \n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-cost --medium\"></div>\n \n \n \n \n \n <div aria-hidden=\"true\" class=\"unfilled-cost --medium\"></div>\n \n \n \n \n \n <div aria-hidden=\"true\" class=\"unfilled-cost --medium\"></div>\n \n \n </div>\n</span>\n </li>\n <li>\n <h4>\n Quality\n </h4>\n <span>\n \n \n \n\n \n \n \n\n <div class=\"score\" aria-label=\"Rated 3 out of 5\">\n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"unfilled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"unfilled-bubble\"></div>\n \n \n </div>\n</span>\n </li>\n <li>\n <h4>\n Speed\n </h4>\n <span>\n \n \n \n\n \n \n \n\n <div class=\"score\" aria-label=\"Rated 4 out of 5\">\n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"unfilled-bubble\"></div>\n \n \n </div>\n</span>\n </li>\n <li>\n <h4>\n Privacy\n </h4>\n <span>\n \n \n \n\n \n \n \n\n <div class=\"score\" aria-label=\"Rated 5 out of 5\">\n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n \n \n <div aria-hidden=\"true\" class=\"filled-bubble\"></div>\n \n \n </div>\n</span>\n </li>\n <li class=\"divider\" aria-hidden=\"true\"></li>\n <li>\n <h4>Last updated</h4>\n <span class=\"date\">\n \n \n 2025-09-05\n \n \n </span>\n </li>\n \n</ul>\n","model_provider_name":"Moonshot AI","internet_access":true,"personalizations":true,"shortcut":null,"is_default_profile":false},"metadata":"<li>\n <span class=\"attribute\">Model</span>\n <span class=\"value\"><i class=\"icon-xs mr-2\"><svg><use href=\"#icon-moonshot\"></use></svg></i>Kimi K2</span>\n</li>\n<li>\n <span class=\"attribute\">Version</span>\n <span class=\"value\">moonshotai/kimi-k2-instruct-0905</span>\n</li>\n<li>\n <span class=\"attribute\">Speed (tok/s)</span>\n <span class=\"value\">162</span>\n</li>\n<li>\n <span class=\"attribute\">Tokens</span>\n <span class=\"value\">3,641</span>\n</li>\n<li>\n <span class=\"attribute\">Cost / Total ($)</span>\n <span class=\"value\">0.009 / 0.009</span>\n</li>\n<li>\n <span class=\"attribute\">End to end time (s)</span>\n <span class=\"value\">9.78</span>\n</li>\n\n","documents":[]}]