JavaScript code example for processing base64 encoding

This article brings you code examples about JavaScript processing base64 encoding. It has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.

Due to project requirements, base64 encoding needs to be processed and recorded again to facilitate subsequent calls.

About base64:

The essence of base64 is to Every 8-bit ASCII code becomes another every 6-bit code, and another reference table is used for corresponding translation.

The following is the js of base64:

var Base64 = {
    // 转码表
    table : [
        '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', '+', '/'
    ],
    UTF16ToUTF8 : function(str) {
        var res = [], len = str.length;
        for (var i = 0; i < len; i++) {
            var code = str.charCodeAt(i);
            if (code > 0x0000 && code <= 0x007F) {
                // 单字节，这里并不考虑0x0000，因为它是空字节
                // U+00000000 – U+0000007F     0xxxxxxx
                res.push(str.charAt(i));
            } else if (code >= 0x0080 && code <= 0x07FF) {
                // 双字节
                // U+00000080 – U+000007FF     110xxxxx 10xxxxxx
                // 110xxxxx
                var byte1 = 0xC0 | ((code >> 6) & 0x1F);
                // 10xxxxxx
                var byte2 = 0x80 | (code & 0x3F);
                res.push(
                    String.fromCharCode(byte1),
                    String.fromCharCode(byte2)
                );
            } else if (code >= 0x0800 && code <= 0xFFFF) {
                // 三字节
                // U+00000800 – U+0000FFFF     1110xxxx 10xxxxxx 10xxxxxx
                // 1110xxxx
                var byte1 = 0xE0 | ((code >> 12) & 0x0F);
                // 10xxxxxx
                var byte2 = 0x80 | ((code >> 6) & 0x3F);
                // 10xxxxxx
                var byte3 = 0x80 | (code & 0x3F);
                res.push(
                    String.fromCharCode(byte1),
                    String.fromCharCode(byte2),
                    String.fromCharCode(byte3)
                );
            } else if (code >= 0x00010000 && code <= 0x001FFFFF) {
                // 四字节
                // U+00010000 – U+001FFFFF     11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
            } else if (code >= 0x00200000 && code <= 0x03FFFFFF) {
                // 五字节
                // U+00200000 – U+03FFFFFF     111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
            } else /** if (code >= 0x04000000 && code <= 0x7FFFFFFF)*/ {
                // 六字节
                // U+04000000 – U+7FFFFFFF     1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
            }
        }

        return res.join(&#39;&#39;);
    },
    UTF8ToUTF16 : function(str) {
        var res = [], len = str.length;
        var i = 0;
        for (var i = 0; i < len; i++) {
            var code = str.charCodeAt(i);
            // 对第一个字节进行判断
            if (((code >> 7) & 0xFF) == 0x0) {
                // 单字节
                // 0xxxxxxx
                res.push(str.charAt(i));
            } else if (((code >> 5) & 0xFF) == 0x6) {
                // 双字节
                // 110xxxxx 10xxxxxx
                var code2 = str.charCodeAt(++i);
                var byte1 = (code & 0x1F) << 6;
                var byte2 = code2 & 0x3F;
                var utf16 = byte1 | byte2;
                res.push(Sting.fromCharCode(utf16));
            } else if (((code >> 4) & 0xFF) == 0xE) {
                // 三字节
                // 1110xxxx 10xxxxxx 10xxxxxx
                var code2 = str.charCodeAt(++i);
                var code3 = str.charCodeAt(++i);
                var byte1 = (code << 4) | ((code2 >> 2) & 0x0F);
                var byte2 = ((code2 & 0x03) << 6) | (code3 & 0x3F);
                var utf16 = ((byte1 & 0x00FF) << 8) | byte2
                res.push(String.fromCharCode(utf16));
            } else if (((code >> 3) & 0xFF) == 0x1E) {
                // 四字节
                // 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
            } else if (((code >> 2) & 0xFF) == 0x3E) {
                // 五字节
                // 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
            } else /** if (((code >> 1) & 0xFF) == 0x7E)*/ {
                // 六字节
                // 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
            }
        }

        return res.join('');
    },
    encode : function(str) {
        if (!str) {
            return '';
        }
        var utf8    = this.UTF16ToUTF8(str); // 转成UTF8
        var i = 0; // 遍历索引
        var len = utf8.length;
        var res = [];
        while (i < len) {
            var c1 = utf8.charCodeAt(i++) & 0xFF;
            res.push(this.table[c1 >> 2]);
            // 需要补2个=
            if (i == len) {
                res.push(this.table[(c1 & 0x3) << 4]);
                res.push(&#39;==&#39;);
                break;
            }
            var c2 = utf8.charCodeAt(i++);
            // 需要补1个=
            if (i == len) {
                res.push(this.table[((c1 & 0x3) << 4) | ((c2 >> 4) & 0x0F)]);
                res.push(this.table[(c2 & 0x0F) << 2]);
                res.push(&#39;=&#39;);
                break;
            }
            var c3 = utf8.charCodeAt(i++);
            res.push(this.table[((c1 & 0x3) << 4) | ((c2 >> 4) & 0x0F)]);
            res.push(this.table[((c2 & 0x0F) << 2) | ((c3 & 0xC0) >> 6)]);
            res.push(this.table[c3 & 0x3F]);
        }

        return res.join('');
    },
    decode : function(str) {
        if (!str) {
            return '';
        }

        var len = str.length;
        var i   = 0;
        var res = [];

        while (i < len) {
            code1 = this.table.indexOf(str.charAt(i++));
            code2 = this.table.indexOf(str.charAt(i++));
            code3 = this.table.indexOf(str.charAt(i++));
            code4 = this.table.indexOf(str.charAt(i++));

            c1 = (code1 << 2) | (code2 >> 4);
            res.push(String.fromCharCode(c1));

            if (code3 != -1) {
                c2 = ((code2 & 0xF) << 4) | (code3 >> 2);
                res.push(String.fromCharCode(c2));
            }
            if (code4 != -1) {
                c3 = ((code3 & 0x3) << 6) | code4;
                res.push(String.fromCharCode(c3));
            }

        }

        return this.UTF8ToUTF16(res.join(&#39;&#39;));
    }
};

Use:

Introduce JS first:

<script src="include/js/Base64.js" type="text/javascript"></script>

Use the method directly:

Base64.decode(content);

About the base64 of the picture:

Set src directly to your base64 in the picture to achieve decoding and display.

The above is the detailed content of JavaScript code example for processing base64 encoding. For more information, please follow other related articles on the PHP Chinese website!