javascript中的Base64、UTF8編碼與解碼詳解

 本文給大家介紹的是javascript中的Base64、UTF8編碼與解碼的函數源碼分享以及使用范例，十分實用，推薦給小伙伴們，希望大家能夠喜歡。

   

Base64編碼說明

　　Base64編碼要求把3個8位字節（3*8=24）轉化為4個6位的字節（4*6=24），之後在6位的前面補兩個0，形成8位一個字節的形式。 如果剩下的字符不足3個字節，則用0填充，輸出字符使用'='，因此編碼後輸出的文本末尾可能會出現1或2個'='。

base64編碼庫：(已驗證可用)

 

代碼如下:
var base64 = (function(){
var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
return {
"encode64":encode64,
"decode64":decode64
}
function encode64(input)
{
input = strUnicode2Ansi(input);
var output = "";
var chr1, chr2, chr3 = "";
var enc1, enc2, enc3, enc4 = "";
var i = 0;
do{
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 +
keyStr.charAt(enc1) +
keyStr.charAt(enc2) +
keyStr.charAt(enc3) +
keyStr.charAt(enc4);
chr1 = chr2 = chr3 = "";
enc1 = enc2 = enc3 = enc4 = "";
}while(i < input.length);
return output;
}
function decode64(input)
{
var output = "";
var chr1, chr2, chr3 = "";
var enc1, enc2, enc3, enc4 = "";
var i = 0;
if(input.length%4!=0)
{
return "";
}
var base64test = /[^A-Za-z0-9+/=]/g;
if (base64test.exec(input))
{
return "";
}
do {
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 = output + String.fromCharCode(chr1);
if (enc3 != 64) {
output+=String.fromCharCode(chr2);
}
if (enc4 != 64) {
output+=String.fromCharCode(chr3);
}
chr1 = chr2 = chr3 = "";
enc1 = enc2 = enc3 = enc4 = "";
} while (i < input.length);
return strAnsi2Unicode(output);
}
function UnicodeChr()
{
return '00A4,00A7,00A8,00B0,00B1,00B7,00D7,00E0,00E1,00E8,00E9,00EA,00EC,00ED,00F2,00F3,00F7,00F9,00FA,00FC,0101,0113,011B,012B,014D,016B,01CE,01D0,01D2,01D4,01D6,01D8,01DA,01DC,02C7,02C9,0391,0392,0393,0394,0395,0396,0397,0398,0399,039A,039B,039C,039D,039E,039F,03A0,03A1,03A3,03A4,03A5,03A6,03A7,03A8,03A9,03B1,03B2,03B3,03B4,03B5,03B6,03B7,03B8,03B9,03BA,03BB,03BC,03BD,03BE,03BF,03C0,03C1,03C3,03C4,03C5,03C6,03C7,03C8,03C9,0401,0410,0411,0412,0413,0414,0415,0416,0417,0418,0419,041A,041B,041C,041D,041E,041F,0420,0421,0422,0423,0424,0425,0426,0427,0428,0429,042A,042B,042C,042D,042E,042F,0430,0431,0432,0433,0434,0435,0436,0437,0438,0439,043A,043B,043C,043D,043E,043F,0440,0441,0442,0443,0444,0445,0446,0447,0448,0449,044A,044B,044C,044D,044E,044F,0451,2014,2016,2018,2019,201C,201D,2026,2030,2032,2033,203B,2103,2116,2160,2161,2162,2163,2164,2165,2166,2167,2168,2169,216A,216B,2190,2191,2192,2193,2208,220F,2211,221A,221D,221E,2220,2225,2227,2228,2229,222A,222B,222E,2234,2235,2236,2237,223D,2248,224C,2260,2261,2264,2265,226E,226F,2299,22A5,2312,2460,2461,2462,2463,2464,2465,2466,2467,2468,2469,2474,2475,2476,2477,2478,2479,247A,247B,247C,247D,247E,247F,2480,2481,2482,2483,2484,2485,2486,2487,2488,2489,248A,248B,248C,248D,248E,248F,2490,2491,2492,2493,2494,2495,2496,2497,2498,2499,249A,249B,2500,2501,2502,2503,2504,2505,2506,2507,2508,2509,250A,250B,250C,250D,250E,250F,2510,2511,2512,2513,2514,2515,2516,2517,2518,2519,251A,251B,251C,251D,251E,251F,2520,2521,2522,2523,2524,2525,2526,2527,2528,2529,252A,252B,252C,252D,252E,252F,2530,2531,2532,2533,2534,2535,2536,2537,2538,2539,253A,253B,253C,253D,253E,253F,2540,2541,2542,2543,2544,2545,2546,2547,2548,2549,254A,254B,25A0,25A1,25B2,25B3,25C6,25C7,25CB,25CE,25CF,2605,2606,2640,2642,3000,3001,3002,3003,3005,3008,3009,300A,300B,300C,300D,300E,300F,3010,3011,3013,3014,3015,3016,3017,3041,3042,3043,3044,3045,3046,3047,3048,3049,304A,304B,304C,304D,304E,304F,3050,3051,3052,3053,3054,3055,3056,3057,3058,3059,305A,305B,305C,305D,305E,305F,3060,3061,3062,3063,3064,3065,3066,3067,3068,3069,306A,306B,306C,306D,306E,306F,3070,3071,3072,3073,3074,3075,3076,3077,3078,3079,307A,307B,307C,307D,307E,307F,3080,3081,3082,3083,3084,3085,3086,3087,3088,3089,308A,308B,308C,308D,308E,308F,3090,3091,3092,3093,30A1,30A2,30A3,30A4,30A5,30A6,30A7,30A8,30A9,30AA,30AB,30AC,30AD,30AE,30AF,30B0,30B1,30B2,30B3,30B4,30B5,30B6,30B7,30B8,30B9,30BA,30BB,30BC,30BD,30BE,30BF,30C0,30C1,30C2,30C3,30C4,30C5,30C6,30C7,30C8,30C9,30CA,30CB,30CC,30CD,30CE,30CF,30D0,30D1,30D2,30D3,30D4,30D5,30D6,30D7,30D8,30D9,30DA,30DB,30DC,30DD,30DE,30DF,30E0,30E1,30E2,30E3,30E4,30E5,30E6,30E7,30E8,30E9,30EA,30EB,30EC,30ED,30EE,30EF,30F0,30F1,30F2,30F3,30F4,30F5,30F6,3105,3106,3107,3108,3109,310A,310B,310C,310D,310E,310F,3110,3111,3112,3113,3114,3115,3116,3117,3118,3119,311A,311B,311C,311D,311E,311F,3120,3121,3122,3123,3124,3125,3126,3127,3128,3129,3220,3221,3222,3223,3224,3225,3226,3227,3228,3229,4E00,4E01,4E03,4E07,4E08,4E09,4E0A,4E0B,4E0C,4E0D,4E0E,4E10,4E11,4E13,4E14,4E15,4E16,4E18,4E19,4E1A,4E1B,4E1C,4E1D,4E1E,4E22,4E24,4E25,4E27,4E28,4E2A,4E2B,4E2C,4E2D,4E30,4E32,4E34,4E36,4E38,4E39,4E3A,4E3B,4E3D,4E3E,4E3F,4E43,4E45,4E47,4E48,4E49,4E4B,4E4C,4E4D,4E4E,4E4F,4E50,4E52,4E53,4E54,4E56,4E58,4E59,4E5C,4E5D,4E5E,4E5F,4E60,4E61,4E66,4E69,4E70,4E71,4E73,4E7E,4E86,4E88,4E89,4E8B,4E8C,4E8D,4E8E,4E8F,4E91,4E92,4E93,4E94,4E95,4E98,4E9A,4E9B,4E9F,4EA0,4EA1,4EA2,4EA4,4EA5,4EA6,4EA7,4EA8,4EA9,4EAB,4EAC,4EAD,4EAE,4EB2,4EB3,4EB5,4EBA,4EBB,4EBF,4EC0,4EC1,4EC2,4EC3,4EC4,4EC5,4EC6,4EC7,4EC9,4ECA,4ECB,4ECD,4ECE,4ED1,4ED3,4ED4,4ED5,4ED6,4ED7,4ED8,4ED9,4EDD,4EDE,4EDF,4EE1,4EE3,4EE4,4EE5,4EE8,4EEA,4EEB,4EEC,4EF0,4EF2,4EF3,4EF5,4EF6,4EF7,4EFB,4EFD,4EFF,4F01,4F09,4F0A,4F0D,4F0E,4F0F,4F10,4F11,4F17,4F18,4F19,4F1A,4F1B,4F1E,4F1F,4F20,4F22,4F24,4F25,4F26,4F27,4F2A,4F2B,4F2F,4F30,4F32,4F34,4F36,4F38,4F3A,4F3C,4F3D,4F43,4F46,4F4D,4F4E,4F4F,4F50,4F51,4F53,4F55,4F57,4F58,4F59,4F5A,4F5B,4F5C,4F5D,4F5E,4F5F,4F60,4F63,4F64,4F65,4F67,4F69,4F6C,4F6F,4F70,4F73,4F74,4F76,4F7B,4F7C,4F7E,4F7F,4F83,4F84,4F88,4F89,4F8B,4F8D,4F8F,4F91,4F94,4F97,4F9B,4F9D,4FA0,4FA3,4FA5,4FA6,4FA7,4FA8,4FA9,4FAA,4FAC,4FAE,4FAF,4FB5,4FBF,4FC3,4FC4,4FC5,4FCA,4FCE,4FCF,4FD0,4FD1,4FD7,4FD8,4FDA,4FDC,4FDD,4FDE,4FDF,4FE1,4FE3,4FE6,4FE8,4FE9,4FEA,4FED,4FEE,4FEF,4FF1,4FF3,4FF8,4FFA,4FFE,500C,500D,500F,5012,5014,5018,5019,501A,501C,501F,5021,5025,5026,5028,5029,502A,502C,502D,502E,503A,503C,503E,5043,5047,5048,504C,504E,504F,5055,505A,505C,5065,506C,5076,5077,507B,507E,507F,5080,5085,5088,508D,50A3,50A5,50A7,50A8,50A9,50AC,50B2,50BA,50BB,50CF,50D6,50DA,50E6,50E7,50EC,50ED,50EE,50F3,50F5,50FB,5106,5107,510B,5112,5121,513F,5140,5141,5143,5144,5145,5146,5148,5149,514B,514D,5151,5154,5155,5156,515A,515C,5162,5165,5168,516B,516C,516D,516E,5170,5171,5173,5174,5175,5176,5177,5178,5179,517B,517C,517D,5180,5181,5182,5185,5188,5189,518C,518D,5192,5195,5196,5197,5199,519B,519C,51A0,51A2,51A4,51A5,51AB,51AC,51AF,51B0,51B1,51B2,51B3,51B5,51B6,51B7,51BB,51BC,51BD,51C0,51C4,51C6,51C7,51C9,51CB,51CC,51CF,51D1,51DB,51DD,51E0,51E1,51E4,51EB,51ED,51EF,51F0,51F3,51F5,51F6,51F8,51F9,51FA,51FB,51FC,51FD,5