Web/API/TextEncoder

TextEncoder takes a stream of code points as input and emits a stream of UTF-8 bytes.

Note: There is a polyfill implementation to support non-UTF-8 text encodings on GitHub.

Example

const encoder = new TextEncoder()
const view = encoder.encode('€')
console.log(view); // Uint8Array(3) [226, 130, 172]

Constructor

TextEncoder(): Returns a newly constructed TextEncoder that will generate a byte stream with UTF-8 encoding.

Properties

The TextEncoder interface doesn't inherit any property.

TextEncoder.prototype.encodingRead only: Always returns "utf-8".

Methods

'The TextEncoder interface doesn't inherit any method.

TextEncoder.prototype.encode(): Takes a USVString as input, and returns a Uint8Array containing UTF-8 encoded text.
TextEncoder.prototype.encodeInto(): Takes a USVString to encode and a destination Uint8Array to put resulting UTF-8 encoded text into, and returns a dictionary object indicating the progress of the encoding. This is potentially more performant than the older encode() method.

Polyfill

The below polyfill is compliant with the standard and therefore only supports UTF-8. It is designed to work in IE5 "out of the box". However, in IE5-IE9, it will return a regular Array instead of a TypedArray. In those cases a polyfill might be impractical for large strings. Finally, note that you should run the below code through a minifier (especially closure compiler) to turn sequences like 0x1e << 3 into 0xf0. These sequences are not already precomputed because they serve to aesthetically illustrate how the polyfill works.

if (typeof TextEncoder === "undefined") {
    TextEncoder=function TextEncoder(){};
    TextEncoder.prototype.encode = function encode(str) {
        "use strict";
        var Len = str.length, resPos = -1;
        // The Uint8Array's length must be at least 3x the length of the string because an invalid UTF-16
        //  takes up the equivelent space of 3 UTF-8 characters to encode it properly. However, Array's
        //  have an auto expanding length and 1.5x should be just the right balance for most uses.
        var resArr = typeof Uint8Array === "undefined" ? new Array(Len * 1.5) : new Uint8Array(Len * 3);
        for (var point=0, nextcode=0, i = 0; i !== Len; ) {
            point = str.charCodeAt(i), i += 1;
            if (point >= 0xD800 && point <= 0xDBFF) {
                if (i === Len) {
                    resArr[resPos += 1] = 0xef/*0b11101111*/; resArr[resPos += 1] = 0xbf/*0b10111111*/;
                    resArr[resPos += 1] = 0xbd/*0b10111101*/; break;
                }
                // https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
                nextcode = str.charCodeAt(i);
                if (nextcode >= 0xDC00 && nextcode <= 0xDFFF) {
                    point = (point - 0xD800) * 0x400 + nextcode - 0xDC00 + 0x10000;
                    i += 1;
                    if (point > 0xffff) {
                        resArr[resPos += 1] = (0x1e/*0b11110*/<<3) | (point>>>18);
                        resArr[resPos += 1] = (0x2/*0b10*/<<6) | ((point>>>12)&0x3f/*0b00111111*/);
                        resArr[resPos += 1] = (0x2/*0b10*/<<6) | ((point>>>6)&0x3f/*0b00111111*/);
                        resArr[resPos += 1] = (0x2/*0b10*/<<6) | (point&0x3f/*0b00111111*/);
                        continue;
                    }
                } else {
                    resArr[resPos += 1] = 0xef/*0b11101111*/; resArr[resPos += 1] = 0xbf/*0b10111111*/;
                    resArr[resPos += 1] = 0xbd/*0b10111101*/; continue;
                }
            }
            if (point <= 0x007f) {
                resArr[resPos += 1] = (0x0/*0b0*/<<7) | point;
            } else if (point <= 0x07ff) {
                resArr[resPos += 1] = (0x6/*0b110*/<<5) | (point>>>6);
                resArr[resPos += 1] = (0x2/*0b10*/<<6)  | (point&0x3f/*0b00111111*/);
            } else {
                resArr[resPos += 1] = (0xe/*0b1110*/<<4) | (point>>>12);
                resArr[resPos += 1] = (0x2/*0b10*/<<6)    | ((point>>>6)&0x3f/*0b00111111*/);
                resArr[resPos += 1] = (0x2/*0b10*/<<6)    | (point&0x3f/*0b00111111*/);
            }
        }
        if (typeof Uint8Array !== "undefined") return resArr.subarray(0, resPos + 1);
        // else // IE 6-9
        resArr.length = resPos + 1; // trim off extra weight
        return resArr;
    };
    TextEncoder.prototype.toString = function(){return "[object TextEncoder]"};
    try { // Object.defineProperty only works on DOM prototypes in IE8
        Object.defineProperty(TextEncoder.prototype,"encoding",{
            get:function(){if(TextEncoder.prototype.isPrototypeOf(this)) return"utf-8";
                           else throw TypeError("Illegal invocation");}
        });
    } catch(e) { /*IE6-8 fallback*/ TextEncoder.prototype.encoding = "utf-8"; }
    if(typeof Symbol!=="undefined")TextEncoder.prototype[Symbol.toStringTag]="TextEncoder";
}

Source: https://github.com/anonyco/FastestSmallestTextEncoderDecoder

Specifications

Specification	Status	Comment
EncodingThe definition of 'TextEncoder' in that specification.	Living Standard	Initial definition.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`TextEncoder` Experimental'	Chrome Full support 38	Edge Full support 79	Firefox Full support 19 Full support 19 Full support 18 Notes' Notes' Firefox 18 implemented an earlier and slightly different version of the specification.	IE No support No	Opera Full support 25	Safari Full support 10.1	WebView Android Full support 38	Chrome Android Full support 38	Firefox Android Full support 19 Full support 19 Full support 18 Notes' Notes' Firefox 18 implemented an earlier and slightly different version of the specification.	Opera Android Full support Yes	Safari iOS Full support 10.3	Samsung Internet Android Full support 3.0
`TextEncoder()` constructor Experimental'	Chrome Full support 53 Notes' Full support 53 Notes' Notes' Does not accept parameters. Supports only `utf-8` encoding. No support 38 — 53 Notes' Notes' Throws `RangeError` exception for unknown encoding types.	Edge Full support 79 Notes' Full support 79 Notes' Notes' Does not accept parameters. Supports only `utf-8` encoding.	Firefox Full support 48 Notes' Full support 48 Notes' Notes' The constructor accepts an encoding type label argument, but the value is ignored. Only `utf-8` encoding is supported. No support 38 — 48 Notes' Notes' If the encoding type label argument is invalid, then a `RangeError` exception is thrown. No support 19 — 38 Notes' Notes' If the encoding type label argument is invalid, then a `TypeError` exception is thrown. Full support 18 Notes' Notes' Firefox 18 implemented an earlier and slightly different version of the specification.	IE No support No	Opera Full support 25	Safari Full support 10.1	WebView Android Full support 38	Chrome Android Full support 38	Firefox Android Full support 48 Notes' Full support 48 Notes' Notes' The constructor accepts an encoding type label argument, but the value is ignored. Only `utf-8` encoding is supported. No support 38 — 48 Notes' Notes' If the encoding type label argument is invalid, then a `RangeError` exception is thrown. No support 19 — 38 Notes' Notes' If the encoding type label argument is invalid, then a `TypeError` exception is thrown. Full support 18 Notes' Notes' Firefox 18 implemented an earlier and slightly different version of the specification.	Opera Android ?	Safari iOS Full support 10.3	Samsung Internet Android Full support 3.0
`encode` Experimental'	Chrome Full support 38	Edge Full support 79	Firefox Full support 19 Full support 19 Full support 18 Notes' Notes' Firefox 18 implemented an earlier and slightly different version of the specification.	IE No support No	Opera Full support 25	Safari Full support 10.1	WebView Android Full support 38	Chrome Android Full support 38	Firefox Android Full support 19 Full support 19 Full support 18 Notes' Notes' Firefox 18 implemented an earlier and slightly different version of the specification.	Opera Android Full support Yes	Safari iOS Full support 10.3	Samsung Internet Android Full support 3.0
`encodeInto` Experimental'	Chrome Full support 74	Edge Full support 79	Firefox Full support 66	IE No support No	Opera No support No	Safari No support No	WebView Android Full support 74	Chrome Android Full support 74	Firefox Android Full support 66	Opera Android No support No	Safari iOS No support No	Samsung Internet Android Full support 11.0
`encoding` Experimental'	Chrome Full support 38	Edge Full support 79	Firefox Full support 19 Full support 19 Full support 18 Notes' Notes' Firefox 18 implemented an earlier and slightly different version of the specification.	IE No support No	Opera Full support 25	Safari Full support 10.1	WebView Android Full support 38	Chrome Android Full support 38	Firefox Android Full support 19 Full support 19 Full support 18 Notes' Notes' Firefox 18 implemented an earlier and slightly different version of the specification.	Opera Android Full support Yes	Safari iOS Full support 10.3	Samsung Internet Android Full support 3.0
Available in workers Experimental'	Chrome Full support 38	Edge Full support 79	Firefox Full support 20	IE No support No	Opera Full support 25	Safari Full support 10.1	WebView Android Full support 38	Chrome Android Full support 38	Firefox Android Full support 20	Opera Android ?	Safari iOS Full support 10.3	Samsung Internet Android Full support 3.0

Legend

Full support: Full support
No support: No support
Compatibility unknown: Compatibility unknown
Experimental. Expect behavior to change in the future.': Experimental. Expect behavior to change in the future.
See implementation notes.': See implementation notes.