window.btoa和window.atob，是浏览器提供的字符串base64编解码。
然而该办法不反对中文字符串的转码。因为转码是针对ASCII码。
能够如下操作实现
window.btoa(window.encodeURIComponent(str))window.decodeURIComponent(window.atob(str))先将中文编码，而后再转base64
留神
无论是escape,encodeURIComponent,encodeURI那种办法，都不是专门针对中文的。
所以，以上办法也会将一些特殊符号@*/+等转码
后果就是除了中文以外的其余字符最终后果和间接btoa的后果不统一。
这里就要看应用场景，只是前端应用没有问题，如果波及到后盾等第三方就不能用了。
罕用的js-base插件办法：encode,
原理如下
将字符串中非acsill字符按固定规定转为两个或者三个长度的UTF-16码
- 要害就是这段代码
const cb_utob = (c) => { if (c.length < 2) { var cc = c.charCodeAt(0); return cc < 0x80 ? c : cc < 0x800 ? (_fromCC(0xc0 | (cc >>> 6)) + _fromCC(0x80 | (cc & 0x3f))) : (_fromCC(0xe0 | ((cc >>> 12) & 0x0f)) + _fromCC(0x80 | ((cc >>> 6) & 0x3f)) + _fromCC(0x80 | (cc & 0x3f))); } else { var cc = 0x10000 + (c.charCodeAt(0) - 0xD800) * 0x400 + (c.charCodeAt(1) - 0xDC00); return (_fromCC(0xf0 | ((cc >>> 18) & 0x07)) + _fromCC(0x80 | ((cc >>> 12) & 0x3f)) + _fromCC(0x80 | ((cc >>> 6) & 0x3f)) + _fromCC(0x80 | (cc & 0x3f))); }};const re_utob = /[\uD800-\uDBFF][\uDC00-\uDFFFF]|[^\x00-\x7F]/g;//utf-8 string return utf-16字符串const utob = (u) => u.replace(re_utob, cb_utob);- 而后就能够转base64了
const btoaPolyfill = (bin) => { // console.log('polyfilled'); let u32, c0, c1, c2, asc = ''; const pad = bin.length % 3; for (let i = 0; i < bin.length;) { if ((c0 = bin.charCodeAt(i++)) > 255 || (c1 = bin.charCodeAt(i++)) > 255 || (c2 = bin.charCodeAt(i++)) > 255) throw new TypeError('invalid character found'); u32 = (c0 << 16) | (c1 << 8) | c2; asc += b64chs[u32 >> 18 & 63] + b64chs[u32 >> 12 & 63] + b64chs[u32 >> 6 & 63] + b64chs[u32 & 63]; } return pad ? asc.slice(0, pad - 3) + "===".substring(pad) : asc;};- 这个办法是插件本人的转base64办法，每个base64字符代表3个bit,办法其实我没太看懂
mdn还有另一种办法
- 原理字符串间接映射ArrayBuffer二进制数组
代码和地址如下：
/* Array of bytes to base64 string decoding */function b64ToUint6 (nChr) { return nChr > 64 && nChr < 91 ? nChr - 65 : nChr > 96 && nChr < 123 ? nChr - 71 : nChr > 47 && nChr < 58 ? nChr + 4 : nChr === 43 ? 62 : nChr === 47 ? 63 : 0;}function base64DecToArr (sBase64, nBlockSize) { var sB64Enc = sBase64.replace(/[^A-Za-z0-9\+\/]/g, ""), nInLen = sB64Enc.length, nOutLen = nBlockSize ? Math.ceil((nInLen * 3 + 1 >>> 2) / nBlockSize) * nBlockSize : nInLen * 3 + 1 >>> 2, aBytes = new Uint8Array(nOutLen); for (var nMod3, nMod4, nUint24 = 0, nOutIdx = 0, nInIdx = 0; nInIdx < nInLen; nInIdx++) { nMod4 = nInIdx & 3; nUint24 |= b64ToUint6(sB64Enc.charCodeAt(nInIdx)) << 18 - 6 * nMod4; if (nMod4 === 3 || nInLen - nInIdx === 1) { for (nMod3 = 0; nMod3 < 3 && nOutIdx < nOutLen; nMod3++, nOutIdx++) { aBytes[nOutIdx] = nUint24 >>> (16 >>> nMod3 & 24) & 255; } nUint24 = 0; } } return aBytes;}/* Base64 string to array encoding */function uint6ToB64 (nUint6) { return nUint6 < 26 ? nUint6 + 65 : nUint6 < 52 ? nUint6 + 71 : nUint6 < 62 ? nUint6 - 4 : nUint6 === 62 ? 43 : nUint6 === 63 ? 47 : 65;}function base64EncArr (aBytes) { var eqLen = (3 - (aBytes.length % 3)) % 3, sB64Enc = ""; for (var nMod3, nLen = aBytes.length, nUint24 = 0, nIdx = 0; nIdx < nLen; nIdx++) { nMod3 = nIdx % 3; /* Uncomment the following line in order to split the output in lines 76-character long: */ /* if (nIdx > 0 && (nIdx * 4 / 3) % 76 === 0) { sB64Enc += "\r\n"; } */ nUint24 |= aBytes[nIdx] << (16 >>> nMod3 & 24); if (nMod3 === 2 || aBytes.length - nIdx === 1) { sB64Enc += String.fromCharCode(uint6ToB64(nUint24 >>> 18 & 63), uint6ToB64(nUint24 >>> 12 & 63), uint6ToB64(nUint24 >>> 6 & 63), uint6ToB64(nUint24 & 63)); nUint24 = 0; } } return eqLen === 0 ? sB64Enc : sB64Enc.substring(0, sB64Enc.length - eqLen) + (eqLen === 1 ? "=" : "==");}MDN-base64