虽然还有一些工作要做，但如果你想要一个高性能的本地解决方案，可以使用一些HTML5函数。

如果你可以把你的数据放到一个Blob中，那么你可以使用FileReader.readAsDataURL()函数来获得一个data:// URL，并砍掉它的前面来获得Base64数据。

你可能必须做进一步的处理，但urldecode数据，因为我不确定是否+字符转义或不为数据:// URL，但这应该是相当微不足道的。

您可以在浏览器中使用btoa()/atob()，但需要一些改进，如https://base64tool.com/uncaught-domexception-btoa-on-window/和https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/btoa所述的UTF字符串支持!

当我使用

btoa("☸☹☺☻☼☾☿"))

我得到:

InvalidCharacterError:要编码的字符串包含Latin1范围之外的字符。

我发现文档，Unicode字符串，提供了一个解决方案如下。

function toBinary(string) { const codeUnits = new Uint16Array(string.length); for (let i = 0; i < codeUnits.length; i++) { codeUnits[i] = string.charCodeAt(i); } return String.fromCharCode(...new Uint8Array(codeUnits.buffer)); } function fromBinary(binary) { const bytes = new Uint8Array(binary.length); for (let i = 0; i < bytes.length; i++) { bytes[i] = binary.charCodeAt(i); } return String.fromCharCode(...new Uint16Array(bytes.buffer)); } const myString = "☸☹☺☻☼☾☿" // console.log(btoa(myString)) // Error InvalidCharacterError: The string to be encoded contains characters outside of the Latin1 range. const converted = toBinary(myString) const encoded = btoa(converted) console.log(encoded) const decoded = atob(encoded) const original = fromBinary(decoded) console.log(original);

JavaScript没有btoa中间步骤(没有库)

在问题标题中你写的是字符串转换，但在问题中你谈论的是二进制数据(图片)，所以这里有一个函数，从PNG图片二进制数据开始进行适当的转换(详细信息和反转转换在这里)。

function bytesArrToBase64(arr) { const abc = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; // base64 alphabet const bin = n => n.toString(2).padStart(8,0); // convert num to 8-bit binary string const l = arr.length let result = ''; for(let i=0; i<=(l-1)/3; i++) { let c1 = i*3+1>=l; // case when "=" is on end let c2 = i*3+2>=l; // case when "=" is on end let chunk = bin(arr[3*i]) + bin(c1? 0:arr[3*i+1]) + bin(c2? 0:arr[3*i+2]); let r = chunk.match(/.{1,6}/g).map((x,j)=> j==3&&c2 ? '=' :(j==2&&c1 ? '=':abc[+('0b'+x)])); result += r.join(''); } return result; } // TEST const pic = [ // PNG binary data 0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0x00, 0x00, 0x00, 0x0d, 0x49, 0x48, 0x44, 0x52, 0x00, 0x00, 0x00, 0x10, 0x00, 0x00, 0x00, 0x10, 0x08, 0x06, 0x00, 0x00, 0x00, 0x1f, 0xf3, 0xff, 0x61, 0x00, 0x00, 0x00, 0x01, 0x73, 0x52, 0x47, 0x42, 0x00, 0xae, 0xce, 0x1c, 0xe9, 0x00, 0x00, 0x01, 0x59, 0x69, 0x54, 0x58, 0x74, 0x58, 0x4d, 0x4c, 0x3a, 0x63, 0x6f, 0x6d, 0x2e, 0x61, 0x64, 0x6f, 0x62, 0x65, 0x2e, 0x78, 0x6d, 0x70, 0x00, 0x00, 0x00, 0x00, 0x00, 0x3c, 0x78, 0x3a, 0x78, 0x6d, 0x70, 0x6d, 0x65, 0x74, 0x61, 0x20, 0x78, 0x6d, 0x6c, 0x6e, 0x73, 0x3a, 0x78, 0x3d, 0x22, 0x61, 0x64, 0x6f, 0x62, 0x65, 0x3a, 0x6e, 0x73, 0x3a, 0x6d, 0x65, 0x74, 0x61, 0x2f, 0x22, 0x20, 0x78, 0x3a, 0x78, 0x6d, 0x70, 0x74, 0x6b, 0x3d, 0x22, 0x58, 0x4d, 0x50, 0x20, 0x43, 0x6f, 0x72, 0x65, 0x20, 0x35, 0x2e, 0x34, 0x2e, 0x30, 0x22, 0x3e, 0x0a, 0x20, 0x20, 0x20, 0x3c, 0x72, 0x64, 0x66, 0x3a, 0x52, 0x44, 0x46, 0x20, 0x78, 0x6d, 0x6c, 0x6e, 0x73, 0x3a, 0x72, 0x64, 0x66, 0x3d, 0x22, 0x68, 0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x77, 0x77, 0x77, 0x2e, 0x77, 0x33, 0x2e, 0x6f, 0x72, 0x67, 0x2f, 0x31, 0x39, 0x39, 0x39, 0x2f, 0x30, 0x32, 0x2f, 0x32, 0x32, 0x2d, 0x72, 0x64, 0x66, 0x2d, 0x73, 0x79, 0x6e, 0x74, 0x61, 0x78, 0x2d, 0x6e, 0x73, 0x23, 0x22, 0x3e, 0x0a, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x3c, 0x72, 0x64, 0x66, 0x3a, 0x44, 0x65, 0x73, 0x63, 0x72, 0x69, 0x70, 0x74, 0x69, 0x6f, 0x6e, 0x20, 0x72, 0x64, 0x66, 0x3a, 0x61, 0x62, 0x6f, 0x75, 0x74, 0x3d, 0x22, 0x22, 0x0a, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x78, 0x6d, 0x6c, 0x6e, 0x73, 0x3a, 0x74, 0x69, 0x66, 0x66, 0x3d, 0x22, 0x68, 0x74, 0x74, 0x70, 0x3a, 0x2f, 0x2f, 0x6e, 0x73, 0x2e, 0x61, 0x64, 0x6f, 0x62, 0x65, 0x2e, 0x63, 0x6f, 0x6d, 0x2f, 0x74, 0x69, 0x66, 0x66, 0x2f, 0x31, 0x2e, 0x30, 0x2f, 0x22, 0x3e, 0x0a, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x3c, 0x74, 0x69, 0x66, 0x66, 0x3a, 0x4f, 0x72, 0x69, 0x65, 0x6e, 0x74, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x3e, 0x31, 0x3c, 0x2f, 0x74, 0x69, 0x66, 0x66, 0x3a, 0x4f, 0x72, 0x69, 0x65, 0x6e, 0x74, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x3e, 0x0a, 0x20, 0x20, 0x20, 0x20, 0x20, 0x20, 0x3c, 0x2f, 0x72, 0x64, 0x66, 0x3a, 0x44, 0x65, 0x73, 0x63, 0x72, 0x69, 0x70, 0x74, 0x69, 0x6f, 0x6e, 0x3e, 0x0a, 0x20, 0x20, 0x20, 0x3c, 0x2f, 0x72, 0x64, 0x66, 0x3a, 0x52, 0x44, 0x46, 0x3e, 0x0a, 0x3c, 0x2f, 0x78, 0x3a, 0x78, 0x6d, 0x70, 0x6d, 0x65, 0x74, 0x61, 0x3e, 0x0a, 0x4c, 0xc2, 0x27, 0x59, 0x00, 0x00, 0x00, 0xf9, 0x49, 0x44, 0x41, 0x54, 0x38, 0x11, 0x95, 0x93, 0x3d, 0x0a, 0x02, 0x41, 0x0c, 0x85, 0xb3, 0xb2, 0x85, 0xb7, 0x10, 0x6c, 0x04, 0x1b, 0x0b, 0x4b, 0x6f, 0xe2, 0x76, 0x1e, 0xc1, 0xc2, 0x56, 0x6c, 0x2d, 0xbc, 0x85, 0xde, 0xc4, 0xd2, 0x56, 0xb0, 0x11, 0xbc, 0x85, 0x85, 0xa0, 0xfb, 0x46, 0xbf, 0xd9, 0x30, 0x33, 0x88, 0x06, 0x76, 0x93, 0x79, 0x93, 0xf7, 0x92, 0xf9, 0xab, 0xcc, 0xec, 0xd9, 0x7e, 0x7f, 0xd9, 0x63, 0x33, 0x8e, 0xf9, 0x75, 0x8c, 0x92, 0xe0, 0x34, 0xe8, 0x27, 0x88, 0xd9, 0xf4, 0x76, 0xcf, 0xb0, 0xaa, 0x45, 0xb2, 0x0e, 0x4a, 0xe4, 0x94, 0x39, 0x59, 0x0c, 0x03, 0x54, 0x14, 0x58, 0xce, 0xbb, 0xea, 0xdb, 0xd1, 0x3b, 0x71, 0x75, 0xb9, 0x9a, 0xe2, 0x7a, 0x7d, 0x36, 0x3f, 0xdf, 0x4b, 0x95, 0x35, 0x09, 0x09, 0xef, 0x73, 0xfc, 0xfa, 0x85, 0x67, 0x02, 0x3e, 0x59, 0x55, 0x31, 0x89, 0x31, 0x56, 0x8c, 0x78, 0xb6, 0x04, 0xda, 0x23, 0x01, 0x01, 0xc8, 0x8c, 0xe5, 0x77, 0x87, 0xbb, 0x65, 0x02, 0x24, 0xa4, 0xad, 0x82, 0xcb, 0x4b, 0x4c, 0x64, 0x59, 0x14, 0xa0, 0x72, 0x40, 0x3f, 0xbf, 0xe6, 0x68, 0xb6, 0x9f, 0x75, 0x08, 0x63, 0xc8, 0x9a, 0x09, 0x02, 0x25, 0x32, 0x34, 0x48, 0x7e, 0xcc, 0x7d, 0x10, 0xaf, 0xa6, 0xd5, 0xd2, 0x1a, 0x3d, 0x89, 0x38, 0xf5, 0xf1, 0x14, 0xb4, 0x69, 0x6a, 0x4d, 0x15, 0xf5, 0xc9, 0xf0, 0x5c, 0x1a, 0x61, 0x8a, 0x75, 0xd1, 0xe8, 0x3a, 0x2c, 0x41, 0x5d, 0x70, 0x41, 0x20, 0x29, 0xf9, 0x9b, 0xb1, 0x37, 0xc5, 0x4d, 0xfc, 0x45, 0x84, 0x7d, 0x08, 0x8f, 0x89, 0x76, 0x54, 0xf1, 0x1b, 0x19, 0x92, 0xef, 0x2c, 0xbe, 0x46, 0x8e, 0xa6, 0x49, 0x5e, 0x61, 0x89, 0xe4, 0x05, 0x5e, 0x4e, 0xa4, 0x5c, 0x10, 0x6e, 0x9f, 0xfc, 0x5b, 0x00, 0x00, 0x00, 0x00, 0x49, 0x45, 0x4e, 0x44, 0xae, 0x42, 0x60, 0x82 ]; let b64pic = bytesArrToBase64(pic); myPic.src = "data:image/png;base64,"+b64pic; msg.innerHTML = "Base64 encoded pic data:<br>" + b64pic; img { zoom: 10; image-rendering: pixelated; } #msg { word-break: break-all; } <img id="myPic"> <code id="msg"></code>

如果你想简单快速地编码base 64，而不考虑可能的兼容性问题，你可以使用turbocommons库。只需下载压缩后的js文件并编写以下代码:

<script src="../yourpathtothelibrary/turbocommons-es5.js"></script>

<script>
    var ConversionUtils = org_turbocommons.ConversionUtils;

    ConversionUtils.stringToBase64('hello');
</script>

你可以在这里查看库是如何完成的代码:

https://github.com/edertone/TurboCommons/blob/master/TurboCommons-TS/src/main/ts/utils/ConversionUtils.ts

更多信息:

https://turboframework.org/en/blog/2022-10-26/encode-decode-base64-strings-javascript-typescript-php

你可以在这里在线测试:

https://turboframework.org/en/app/stringutils/base64-encode

如果您正在使用Dojo。它为我们提供了编码或解码为Base64的直接方法。

试试这个:

使用dojox.encoding.base64对字节数组进行编码:

var str = dojox.encoding.base64.encode(myByteArray);

解码一个base64编码的字符串:

var bytes = dojox.encoding.base64.decode(str);