浏览器和nodejs上有没有可以将base64字符串转换为utf8字符串的API？

Question

const atob = (encodedString) => Buffer.from(encodedString, 'base64').toString('latin1')

Is there an API that can be used normally in nodejs and browsers that can help me convert base64 to utf8 string？

In node.js, we can write:

const base64ToUtf8 = (encodedString) => Buffer.from(encodedString, 'base64').toString('utf8')

I need to use this function to process base64 encoded utf8 data-uri in node.js and browser.

Answer 1

This node-js code reads the data encoded in this base64 string "as UTF-8" . Beware it's not the same as converting "to an UTF-8 string", since JavaScript only supports UCS-2 and UTF-16 strings.

This nitpick passed, there are many methods to do the same as this code in a browser.

The cleanest is to first decode this base64 string in an ArrayBuffer and then read that ArrayBuffer as string, just like your node code:

 const b64 = "wqFIb2xhIG5pw7FvcyE="; const buf = base64ToBuf(b64); const txt = new TextDecoder().decode(buf); console.log(txt); function base64ToBuf(str) { const binStr = atob(str); const len = binStr.length; const arr = new Uint8Array(len); for (let i = 0; i < len; i++) { arr[i] = binStr.charCodeAt(i); } return arr; }

An other, shorter in code, but implying more IO is to fetch it as text:

 const b64 = "wqFIb2xhIG5pw7FvcyE="; fetch('data:text;base64,' + b64) .then(r => r.text()) .then(txt => console.log(txt));

And you could also make use of the FileReader API's readAsText() , which might be useful in case you want to support more encodings than utf-8.

 const b64 = "wqFIb2xhIG5pw7FvcyE="; const blob = base64ToBlob(b64); const reader = new FileReader(); reader.onload = e => { const txt = reader.result; console.log(txt); }; reader.readAsText(blob, "utf8"); function base64ToBlob(str) { const binStr = atob(str); const len = binStr.length; const arr = new Uint8Array(len); for (let i = 0; i < len; i++) { arr[i] = binStr.charCodeAt(i); } return new Blob([arr]); }

There is also the new Blob.text() that does convert to utf-8 directly, but from a base64 string, there is very little interest in going that road. Still for the curious:

 const b64 = "wqFIb2xhIG5pw7FvcyE="; const blob = base64ToBlob(b64); blob.text().then(txt => console.log(txt)); function base64ToBlob(str) { const binStr = atob(str); const len = binStr.length; const arr = new Uint8Array(len); for (let i = 0; i < len; i++) { arr[i] = binStr.charCodeAt(i); } return new Blob([arr]); }