小程序base64 utf-8解码

复制过去直接把调用base64_decode(input) 传入需要解码的字符串

base64_decode(input) { // 解码，配合decodeURIComponent使用
				var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
				var output = "";
				var chr1, chr2, chr3;
				var enc1, enc2, enc3, enc4;
				var i = 0;
				input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
				while (i < input.length) {
					enc1 = base64EncodeChars.indexOf(input.charAt(i++));
					enc2 = base64EncodeChars.indexOf(input.charAt(i++));
					enc3 = base64EncodeChars.indexOf(input.charAt(i++));
					enc4 = base64EncodeChars.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 = output + String.fromCharCode(chr2);
					}
					if (enc4 != 64) {
						output = output + String.fromCharCode(chr3);
					}
				}
				return this.utf8_decode(output);
			},
			utf8_decode(utftext) { // utf-8解码
				var string = '';
				let i = 0;
				let c = 0;
				let c1 = 0;
				let 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;
					}
				}
				console.log('string', string);
				return string;
			},