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。
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
我已经手工重写了这些编码和解码方法,除了十六进制的编码方法外,它们都是模块化格式的,以便跨平台/浏览器兼容,并且还具有真正的私有作用域,如果它们由于速度而存在,则使用btoa和atob,而不是利用自己的编码:
https://gist.github.com/Nijikokun/5192472
用法:
base64.encode(/* String */);
base64.decode(/* String */);
utf8.encode(/* String */);
utf8.decode(/* String */);
其他回答
2022年弃用警告更新
我在我的vscode上看到了弃用警告
This function is only provided for compatibility with legacy web platform APIs and should never be used in new code,
because they use strings to represent binary data and predate the introduction of typed arrays in JavaScript.
For code running using Node.js APIs,
converting between base64-encoded strings and binary data should be performed using Buffer.from(str, 'base64') andbuf.toString('base64').
在搜索了一些之后,我发现这个问题说它没有被弃用
https://github.com/microsoft/TypeScript/issues/45566
所以解决web JS弃用警告的方法是使用window.btoa 警告就会消失。
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;
}
这是一个缩小的填充窗口。Atob + window.btoa:
(function(){function t(t){this.message=t}var e="undefined"!=typeof exports?exports:this,r="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";t.prototype=Error(),t.prototype.name="InvalidCharacterError",e.btoa||(e.btoa=function(e){for(var o,n,a=0,i=r,c="";e.charAt(0|a)||(i="=",a%1);c+=i.charAt(63&o>>8-8*(a%1))){if(n=e.charCodeAt(a+=.75),n>255)throw new t("'btoa' failed: The string to be encoded contains characters outside of the Latin1 range.");o=o<<8|n}return c}),e.atob||(e.atob=function(e){if(e=e.replace(/=+$/,""),1==e.length%4)throw new t("'atob' failed: The string to be decoded is not correctly encoded.");for(var o,n,a=0,i=0,c="";n=e.charAt(i++);~n&&(o=a%4?64*o+n:n,a++%4)?c+=String.fromCharCode(255&o>>(6&-2*a)):0)n=r.indexOf(n);return c})})();
(function (root, factory) {
if (typeof define === 'function' && define.amd) {
// AMD. Register as an anonymous module.
define([], function() {factory(root);});
} else factory(root);
// node.js has always supported base64 conversions, while browsers that support
// web workers support base64 too, but you may never know.
})(typeof exports !== "undefined" ? exports : this, function(root) {
if (root.atob) {
// Some browsers' implementation of atob doesn't support whitespaces
// in the encoded string (notably, IE). This wraps the native atob
// in a function that strips the whitespaces.
// The original function can be retrieved in atob.original
try {
root.atob(" ");
} catch(e) {
root.atob = (function(atob) {
var func = function(string) {
return atob(String(string).replace(/[\t\n\f\r ]+/g, ""));
};
func.original = atob;
return func;
})(root.atob);
}
return;
}
// base64 character set, plus padding character (=)
var b64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
// Regular expression to check formal correctness of base64 encoded strings
b64re = /^(?:[A-Za-z\d+\/]{4})*?(?:[A-Za-z\d+\/]{2}(?:==)?|[A-Za-z\d+\/]{3}=?)?$/;
root.btoa = function(string) {
string = String(string);
var bitmap, a, b, c,
result = "", i = 0,
rest = string.length % 3; // To determine the final padding
for (; i < string.length;) {
if ((a = string.charCodeAt(i++)) > 255
|| (b = string.charCodeAt(i++)) > 255
|| (c = string.charCodeAt(i++)) > 255)
throw new TypeError("Failed to execute 'btoa' on 'Window': The string to be encoded contains characters outside of the Latin1 range.");
bitmap = (a << 16) | (b << 8) | c;
result += b64.charAt(bitmap >> 18 & 63) + b64.charAt(bitmap >> 12 & 63)
+ b64.charAt(bitmap >> 6 & 63) + b64.charAt(bitmap & 63);
}
// If there's need of padding, replace the last 'A's with equal signs
return rest ? result.slice(0, rest - 3) + "===".substring(rest) : result;
};
root.atob = function(string) {
// atob can work with strings with whitespaces, even inside the encoded part,
// but only \t, \n, \f, \r and ' ', which can be stripped.
string = String(string).replace(/[\t\n\f\r ]+/g, "");
if (!b64re.test(string))
throw new TypeError("Failed to execute 'atob' on 'Window': The string to be decoded is not correctly encoded.");
// Adding the padding if missing, for semplicity
string += "==".slice(2 - (string.length & 3));
var bitmap, result = "", r1, r2, i = 0;
for (; i < string.length;) {
bitmap = b64.indexOf(string.charAt(i++)) << 18 | b64.indexOf(string.charAt(i++)) << 12
| (r1 = b64.indexOf(string.charAt(i++))) << 6 | (r2 = b64.indexOf(string.charAt(i++)));
result += r1 === 64 ? String.fromCharCode(bitmap >> 16 & 255)
: r2 === 64 ? String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255)
: String.fromCharCode(bitmap >> 16 & 255, bitmap >> 8 & 255, bitmap & 255);
}
return result;
};
});
完整版https://github.com/MaxArt2501/base64-js/blob/master/base64.js
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);
这是一个helper funktion来编码到base64url:
base64url (s) {
var to64url = btao(s);
// Replace non-url compatible chars with base64url standard chars and remove leading =
return to64url.replace(/\+/g, '_').replace(/\//g, '-').replace(/=+$/g, '');
}