微信小程序中javascript将String进行Base64编码并UTF-8格式输出

提供一种Base64编码,并输出UTF-8格式的BASE64编码方式。本程序在微信小程序开发工具中已经测试通过。

 Base64代码：

[code]
(function(){
var BASE64_MAPPING = [
'A','B','C','D','E','F','G','H',
'I','J','K','L','M','N','O','P',
'Q','R','S','T','U','V','W','X',
'Y','Z','a','b','c','d','e','f',
'g','h','i','j','k','l','m','n',
'o','p','q','r','s','t','u','v',
'w','x','y','z','0','1','2','3',
'4','5','6','7','8','9','+','/'
];

/**
*ascii convert to binary
*/
var _toBinary = function(ascii){
var binary = new Array();
while(ascii > 0){
var b = ascii%2;
ascii = Math.floor(ascii/2);
binary.push(b);
}
/*
var len = binary.length;
if(6-len > 0){
for(var i = 6-len ; i > 0 ; --i){
binary.push(0);
}
}*/
binary.reverse();
return binary;
};

/**
*binary convert to decimal
*/
var _toDecimal  = function(binary){
var dec = 0;
var p = 0;
for(var i = binary.length-1 ; i >= 0 ; --i){
var b = binary[i];
if(b == 1){
dec += Math.pow(2 , p);
}
++p;
}
return dec;
};

/**
*unicode convert to utf-8
*/
var _toUTF8Binary = function(c , binaryArray){
var mustLen = (8-(c+1)) + ((c-1)*6);
var fatLen = binaryArray.length;
var diff = mustLen - fatLen;
while(--diff >= 0){
binaryArray.unshift(0);
}
var binary = [];
var _c = c;
while(--_c >= 0){
binary.push(1);
}
binary.push(0);
var i = 0 , len = 8 - (c+1);
for(; i < len ; ++i){
binary.push(binaryArray[i]);
}

for(var j = 0 ; j < c-1 ; ++j){
binary.push(1);
binary.push(0);
var sum = 6;
while(--sum >= 0){
binary.push(binaryArray[i++]);
}
}
return binary;
};

var __BASE64 = {
/**
*BASE64 Encode
*/
encoder:function(str){
var base64_Index = [];
var binaryArray = [];
for(var i = 0 , len = str.length ; i < len ; ++i){
var unicode = str.charCodeAt(i);
var _tmpBinary = _toBinary(unicode);
if(unicode < 0x80){
var _tmpdiff = 8 - _tmpBinary.length;
while(--_tmpdiff >= 0){
_tmpBinary.unshift(0);
}
binaryArray = binaryArray.concat(_tmpBinary);
}else if(unicode >= 0x80 && unicode <= 0x7FF){
binaryArray = binaryArray.concat(_toUTF8Binary(2 , _tmpBinary));
}else if(unicode >= 0x800 && unicode <= 0xFFFF){//UTF-8 3byte
binaryArray = binaryArray.concat(_toUTF8Binary(3 , _tmpBinary));
}else if(unicode >= 0x10000 && unicode <= 0x1FFFFF){//UTF-8 4byte
binaryArray = binaryArray.concat(_toUTF8Binary(4 , _tmpBinary));
}else if(unicode >= 0x200000 && unicode <= 0x3FFFFFF){//UTF-8 5byte
binaryArray = binaryArray.concat(_toUTF8Binary(5 , _tmpBinary));
}else if(unicode >= 4000000 && unicode <= 0x7FFFFFFF){//UTF-8 6byte
binaryArray = binaryArray.concat(_toUTF8Binary(6 , _tmpBinary));
}
}

var extra_Zero_Count = 0;
for(var i = 0 , len = binaryArray.length ; i < len ; i+=6){
var diff = (i+6)-len;
if(diff == 2){
extra_Zero_Count = 2;
}else if(diff == 4){
extra_Zero_Count = 4;
}
//if(extra_Zero_Count > 0){
//	len += extra_Zero_Count+1;
//}
var _tmpExtra_Zero_Count = extra_Zero_Count;
while(--_tmpExtra_Zero_Count >= 0){
binaryArray.push(0);
}
base64_Index.push(_toDecimal(binaryArray.slice(i , i+6)));
}

var base64 = '';
for(var i = 0 , len = base64_Index.length ; i < len ; ++i){
base64 += BASE64_MAPPING[base64_Index[i]];
}

for(var i = 0 , len = extra_Zero_Count/2 ; i < len ; ++i){
base64 += '=';
}
return base64;
},
/**
*BASE64  Decode for UTF-8
*/
decoder : function(_base64Str){
var _len = _base64Str.length;
var extra_Zero_Count = 0;
/**
*计算在进行BASE64编码的时候，补了几个0
*/
if(_base64Str.charAt(_len-1) == '='){
//alert(_base64Str.charAt(_len-1));
//alert(_base64Str.charAt(_len-2));
if(_base64Str.charAt(_len-2) == '='){//两个等号说明补了4个0
extra_Zero_Count = 4;
_base64Str = _base64Str.substring(0 , _len-2);
}else{//一个等号说明补了2个0
extra_Zero_Count = 2;
_base64Str = _base64Str.substring(0 , _len - 1);
}
}

var binaryArray = [];
for(var i = 0 , len = _base64Str.length; i < len ; ++i){
var c = _base64Str.charAt(i);
for(var j = 0 , size = BASE64_MAPPING.length ; j < size ; ++j){
if(c == BASE64_MAPPING[j]){
var _tmp = _toBinary(j);
/*不足6位的补0*/
var _tmpLen = _tmp.length;
if(6-_tmpLen > 0){
for(var k = 6-_tmpLen ; k > 0 ; --k){
_tmp.unshift(0);
}
}
binaryArray = binaryArray.concat(_tmp);
break;
}
}
}

if(extra_Zero_Count > 0){
binaryArray = binaryArray.slice(0 , binaryArray.length - extra_Zero_Count);
}

var unicode = [];
var unicodeBinary = [];
for(var i = 0 , len = binaryArray.length ; i < len ; ){
if(binaryArray[i] == 0){
unicode=unicode.concat(_toDecimal(binaryArray.slice(i,i+8)));
i += 8;
}else{
var sum = 0;
while(i < len){
if(binaryArray[i] == 1){
++sum;
}else{
break;
}
++i;
}
unicodeBinary = unicodeBinary.concat(binaryArray.slice(i+1 , i+8-sum));
i += 8 - sum;
while(sum > 1){
unicodeBinary = unicodeBinary.concat(binaryArray.slice(i+2 , i+8));
i += 8;
--sum;
}
unicode = unicode.concat(_toDecimal(unicodeBinary));
unicodeBinary = [];
}
}
return unicode;
}
};

//window.BASE64 = __BASE64;
module.exports = {
CusBASE64: __BASE64
}
})();

调用方式：

[code]//文件引用
var CusBase64 = require('base64.js');
//函数调用
var result=CusBase64.CusBASE64.encoder(data);

转自：https://www.geek-share.com/detail/2710603360.html