我有一个PHP脚本，可以将PNG图像编码为Base64字符串。
我想用JavaScript做同样的事情。我知道如何打开文件，但我不知道如何进行编码。我不习惯使用二进制数据。
当前回答
从下面的评论(由SET和Stefan Steiger)接受的答案，这里是一个快速总结如何编码/解码一个字符串到Base64，而不需要一个库。
str = "The quick brown fox jumps over the lazy dog";
b64 = btoa(unescape(encodeURIComponent(str)));
str = decodeURIComponent(escape(window.atob(b64)));
纯JavaScript演示
const input = document.getElementsByTagName('input')[0]; const btnConv = document.getElementById('btnConv'); const btnDeConv = document.getElementById('btnDeConv'); input.value = "The quick brown fox jumps over the lazy dog"; btnConv.addEventListener('click', () => { const txt = input.value; const b64 = btoa(unescape(encodeURIComponent(txt))); input.value = b64; btnDeConv.style.display = 'block'; btnConv.style.display = 'none'; }); btnDeConv.addEventListener('click', () => { var b64 = input.value; var txt = decodeURIComponent(escape(window.atob(b64))); input.value = txt; btnConv.style.display = 'block'; btnDeConv.style.display = 'none'; }); input{width:500px;} #btnDeConv{display:none;} <div><input type="text" /></div> <button id="btnConv">Convert</button> <button id="btnDeConv">DeConvert</button>
.
jQuery演示(使用jQuery库进行显示，但不用于编码/解码)
str = "The quick brown fox jumps over the lazy dog"; $('input').val(str); $('#btnConv').click(function(){ var txt = $('input').val(); var b64 = btoa(unescape(encodeURIComponent(txt))); $('input').val(b64); $('#btnDeConv').show(); }); $('#btnDeConv').click(function(){ var b64 = $('input').val(); var txt = decodeURIComponent(escape(window.atob(b64))); $('input').val(txt); }); #btnDeConv{display:none;} <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <input type="text" /> <button id="btnConv">Convert</button> <button id="btnDeConv">DeConvert</button>
还看到:
Base64 - MDN Web文档 在JavaScript中判断一个字符串是否在Base64中
其他回答
基本上，我只是稍微清理了一下原始代码，这样JSLint就不会抱怨太多了，而且我把注释中标记为私有的方法实际上变成了私有的。我还添加了我在自己的项目中需要的两个方法，即decodeToHex和encodeFromHex。
代码:
var Base64 = (function() {
"use strict";
var _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
var _utf8_encode = function (string) {
var utftext = "", c, n;
string = string.replace(/\r\n/g,"\n");
for (n = 0; n < string.length; n++) {
c = string.charCodeAt(n);
if (c < 128) {
utftext += String.fromCharCode(c);
} else if((c > 127) && (c < 2048)) {
utftext += String.fromCharCode((c >> 6) | 192);
utftext += String.fromCharCode((c & 63) | 128);
} else {
utftext += String.fromCharCode((c >> 12) | 224);
utftext += String.fromCharCode(((c >> 6) & 63) | 128);
utftext += String.fromCharCode((c & 63) | 128);
}
}
return utftext;
};
var _utf8_decode = function (utftext) {
var string = "", i = 0, c = 0, c1 = 0, c2 = 0;
while ( i < utftext.length ) {
c = utftext.charCodeAt(i);
if (c < 128) {
string += String.fromCharCode(c);
i++;
} else if((c > 191) && (c < 224)) {
c1 = utftext.charCodeAt(i+1);
string += String.fromCharCode(((c & 31) << 6) | (c1 & 63));
i += 2;
} else {
c1 = utftext.charCodeAt(i+1);
c2 = utftext.charCodeAt(i+2);
string += String.fromCharCode(((c & 15) << 12) | ((c1 & 63) << 6) | (c2 & 63));
i += 3;
}
}
return string;
};
var _hexEncode = function(input) {
var output = '', i;
for(i = 0; i < input.length; i++) {
output += input.charCodeAt(i).toString(16);
}
return output;
};
var _hexDecode = function(input) {
var output = '', i;
if(input.length % 2 > 0) {
input = '0' + input;
}
for(i = 0; i < input.length; i = i + 2) {
output += String.fromCharCode(parseInt(input.charAt(i) + input.charAt(i + 1), 16));
}
return output;
};
var encode = function (input) {
var output = "", chr1, chr2, chr3, enc1, enc2, enc3, enc4, i = 0;
input = _utf8_encode(input);
while (i < input.length) {
chr1 = input.charCodeAt(i++);
chr2 = input.charCodeAt(i++);
chr3 = input.charCodeAt(i++);
enc1 = chr1 >> 2;
enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
enc4 = chr3 & 63;
if (isNaN(chr2)) {
enc3 = enc4 = 64;
} else if (isNaN(chr3)) {
enc4 = 64;
}
output += _keyStr.charAt(enc1);
output += _keyStr.charAt(enc2);
output += _keyStr.charAt(enc3);
output += _keyStr.charAt(enc4);
}
return output;
};
var decode = function (input) {
var output = "", chr1, chr2, chr3, enc1, enc2, enc3, enc4, i = 0;
input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
while (i < input.length) {
enc1 = _keyStr.indexOf(input.charAt(i++));
enc2 = _keyStr.indexOf(input.charAt(i++));
enc3 = _keyStr.indexOf(input.charAt(i++));
enc4 = _keyStr.indexOf(input.charAt(i++));
chr1 = (enc1 << 2) | (enc2 >> 4);
chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
chr3 = ((enc3 & 3) << 6) | enc4;
output += String.fromCharCode(chr1);
if (enc3 !== 64) {
output += String.fromCharCode(chr2);
}
if (enc4 !== 64) {
output += String.fromCharCode(chr3);
}
}
return _utf8_decode(output);
};
var decodeToHex = function(input) {
return _hexEncode(decode(input));
};
var encodeFromHex = function(input) {
return encode(_hexDecode(input));
};
return {
'encode': encode,
'decode': decode,
'decodeToHex': decodeToHex,
'encodeFromHex': encodeFromHex
};
}());
请注意，这不适用于原始的Unicode字符串!请参阅这里的Unicode部分。
编码语法
var encodedData = window.btoa（stringToEncode）;
解码语法
var decodedData = window.atob（encodedData）;
在_utf8_decode的两个实现中都有一些错误。C1和c2由于var语句的错误使用被赋值为全局变量，c3根本没有初始化或声明。
它可以工作，但这些变量将覆盖该函数之外的任何具有相同名称的现有变量。
这里有一个版本不会这样做:
// private method for UTF-8 decoding
_utf8_decode : function (utftext) {
var string = "";
var i = 0;
var c = 0, c1 = 0, c2 = 0;
while ( i < utftext.length ) {
c = utftext.charCodeAt(i);
if (c < 128) {
string += String.fromCharCode(c);
i++;
}
else if((c > 191) && (c < 224)) {
c1 = utftext.charCodeAt(i+1);
string += String.fromCharCode(((c & 31) << 6) | (c1 & 63));
i += 2;
}
else {
c1 = utftext.charCodeAt(i+1);
c2 = utftext.charCodeAt(i+2);
string += String.fromCharCode(((c & 15) << 12) | ((c1 & 63) << 6) | (c2 & 63));
i += 3;
}
}
return string;
}
从这里开始:
/**
*
* Base64 encode / decode
* http://www.webtoolkit.info/
*
**/
var Base64 = {
// private property
_keyStr : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
// public method for encoding
encode : function (input) {
var output = "";
var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
var i = 0;
input = Base64._utf8_encode(input);
while (i < input.length) {
chr1 = input.charCodeAt(i++);
chr2 = input.charCodeAt(i++);
chr3 = input.charCodeAt(i++);
enc1 = chr1 >> 2;
enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
enc4 = chr3 & 63;
if (isNaN(chr2)) {
enc3 = enc4 = 64;
} else if (isNaN(chr3)) {
enc4 = 64;
}
output = output +
this._keyStr.charAt(enc1) + this._keyStr.charAt(enc2) +
this._keyStr.charAt(enc3) + this._keyStr.charAt(enc4);
}
return output;
},
// public method for decoding
decode : function (input) {
var output = "";
var chr1, chr2, chr3;
var enc1, enc2, enc3, enc4;
var i = 0;
input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
while (i < input.length) {
enc1 = this._keyStr.indexOf(input.charAt(i++));
enc2 = this._keyStr.indexOf(input.charAt(i++));
enc3 = this._keyStr.indexOf(input.charAt(i++));
enc4 = this._keyStr.indexOf(input.charAt(i++));
chr1 = (enc1 << 2) | (enc2 >> 4);
chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
chr3 = ((enc3 & 3) << 6) | enc4;
output = output + String.fromCharCode(chr1);
if (enc3 != 64) {
output = output + String.fromCharCode(chr2);
}
if (enc4 != 64) {
output = output + String.fromCharCode(chr3);
}
}
output = Base64._utf8_decode(output);
return output;
},
// private method for UTF-8 encoding
_utf8_encode : function (string) {
string = string.replace(/\r\n/g,"\n");
var utftext = "";
for (var n = 0; n < string.length; n++) {
var c = string.charCodeAt(n);
if (c < 128) {
utftext += String.fromCharCode(c);
}
else if((c > 127) && (c < 2048)) {
utftext += String.fromCharCode((c >> 6) | 192);
utftext += String.fromCharCode((c & 63) | 128);
}
else {
utftext += String.fromCharCode((c >> 12) | 224);
utftext += String.fromCharCode(((c >> 6) & 63) | 128);
utftext += String.fromCharCode((c & 63) | 128);
}
}
return utftext;
},
// private method for UTF-8 decoding
_utf8_decode : function (utftext) {
var string = "";
var i = 0;
var c = c1 = c2 = 0;
while ( i < utftext.length ) {
c = utftext.charCodeAt(i);
if (c < 128) {
string += String.fromCharCode(c);
i++;
}
else if((c > 191) && (c < 224)) {
c2 = utftext.charCodeAt(i+1);
string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
i += 2;
}
else {
c2 = utftext.charCodeAt(i+1);
c3 = utftext.charCodeAt(i+2);
string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
i += 3;
}
}
return string;
}
}
此外，搜索“JavaScript base64 encoding”会出现许多其他选项，上面是第一个。
您可以使用btoa(从Base64)和atob(从Base64)。
对于ie9及以下版本，请尝试jquery-base64插件:
$.base64.encode("this is a test");
$.base64.decode("dGhpcyBpcyBhIHRlc3Q=");
