来源
《JavaScript语言精粹（修订版）》
代码
1 <!DOCTYPE html>
2 <html>
3
4 <head>
5 <meta charset="UTF-8">
6 <title></title>
7 </head>
8
9 <body>
10 <script>
11 var json_parse = function () {
12 var
13 at,
14 ch,
15 escapee = {
16 ‘"‘: ‘"‘,
17 ‘\\‘: ‘\\‘,
18 ‘/‘: ‘/‘,
19 b: ‘b‘,
20 f: ‘\f‘,
21 n: ‘\n‘,
22 r: ‘\r‘,
23 t: ‘\t‘
24 },
25 text,
26 // 抛出异常
27 error = function (m) {
28 throw {
29 name: ‘SyntaxError‘,
30 message: m,
31 at: at,
32 text: text
33 }
34 },
35 // 获取下一个字符
36 next = function (c) {
37 if (c && c !== ch) {
38 error(`Expected ${c} instead of ${ch}`);
39 }
40 ch = text.charAt(at);
41 at += 1;
42 return ch;
43 },
44 // 解析一个数字值
45 number = function () {
46 var number, string = ‘‘;
47 // 负号
48 if (ch === ‘-‘) {
49 string = ‘-‘,
50 next(‘-‘)
51 }
52 // 整数
53 while (ch >= ‘0‘ && ch <= ‘9‘) {
54 string += ch;
55 next();
56 }
57 // 小数
58 if (ch === ‘.‘) {
59 string += ‘.‘;
60 while (next() && ch >= ‘0‘ && ch <= ‘9‘) {
61 string += ch;
62 }
63 }
64 // 指数
65 if (ch === ‘e‘ || ch === ‘E‘) {
66 string += ch;
67 next();
68 if (ch === ‘-‘ || ch === ‘+‘) {
69 string += ch;
70 next();
71 }
72 while (ch >= ‘0‘ && ch <= ‘9‘) {
73 string += ch;
74 next();
75 }
76 }
77 number = +string;
78 if (isNaN(number)) {
79 error(‘Bad number‘)
80 } else {
81 return number;
82 }
83 },
84 // 解析一个字符串值
85 string = function () {
86 var hex,
87 i,
88 string = ‘‘,
89 uffff;
90 // 字符串必须以双引号开始
91 if (ch === ‘"‘) {
92 while (next()) {
93 if (ch === ‘"‘) {
94 next();
95 return string;
96 } else if (ch === ‘\\‘) {
97 next();
98 // unicode码
99 if (ch === ‘u‘) {
100 uffff = 0;
101 for (i = 0; i < 4; i++) {
102 hex = parseInt(next(), 16);
103 if (!isFinite(hex)) {
104 break;
105 }
106 ufff = ufff * 16 + hex;
107 }
108 string += String.fromCharCode(ufff)
109 }
110 else if (typeof escapee[ch] === ‘string‘) { // 转义字符
111 string += escapee[ch]
112 } else {
113 break;
114 }
115 } else {
116 string += ch;
117 }
118 }
119 }
120 error(‘Bac string‘);
121 },
122 // 跳过空白
123 white = function () {
124 while (ch && ch <= ‘ ‘) {
125 next();
126 }
127 },
128 // 解析 true、false、null
129 word = function () {
130 switch (ch) {
131 case ‘t‘:
132 next(‘t‘);
133 next(‘r‘);
134 next(‘u‘);
135 next(‘e‘);
136 return true;
137 case ‘f‘:
138 next(‘f‘);
139 next(‘a‘);
140 next(‘l‘);
141 next(‘s‘);
142 next(‘e‘);
143 return true;
144 case ‘n‘:
145 next(‘n‘);
146 next(‘u‘);
147 next(‘l‘);
148 next(‘l‘);
149 return true;
150 }
151 error(`Unexpected ${ch}`)
152 },
153 // 解析一个数组值
154 array = function () {
155 var array = [];
156 if (ch === ‘[‘) {
157 next(‘[‘);
158 white();
159 if (ch === ‘]‘) {
160 next(‘]‘);
161 return array;
162 }
163 while (ch) {
164 array.push(value());
165 white();
166 if (ch === ‘]‘) {
167 next(‘]‘);
168 return array;
169 }
170 next(‘,‘);
171 white();
172 }
173 }
174 error(‘Bad array‘);
175 },
176 // 解析一个对象值
177 object = function () {
178 var key, object = {};
179 if (ch === ‘{‘) {
180 next(‘{‘);
181 white();
182 if (ch === ‘}‘) {
183 next(‘}‘);
184 return object;
185 }
186 while (ch) {
187 key = string();
188 white();
189 next(‘:‘);
190 object[key] = value();
191 white();
192 if (ch === ‘}‘) {
193 next(‘}‘);
194 return object;
195 }
196 next(‘,‘);
197 white();
198 }
199 }
200 error(‘Bad object‘);
201 },
202 // 解析一个JSON值。它可以是对象、数组、字符串、数字、一个词。
203 value = function () {
204 white();
205 switch (ch) {
206 case ‘{‘:
207 return object();
208 case ‘[‘:
209 return array();
210 case ‘"‘:
211 return string();
212 case ‘-‘:
213 return number;
214 default:
215 return ch >= ‘0‘ && ch <= ‘9‘ ? number() : word();
216 }
217 };
218 // 返回json_parse函数
219 return function (source, reviver) {
220 var result;
221 text = source;
222 at = 0;
223 ch = ‘ ‘;
224 result = value();
225 white();
226 if (ch) { // 多余的非空白字符
227 error(‘Syntax error‘);
228 }
229 return typeof reviver === ‘function‘ ? function walk(holder, key) {
230 var k, v, value = holder[key];
231 if (value && typeof value === ‘object‘) {
232 // 递归处理对象的属性
233 for (k in value) {
234 if (Object.hasOwnProperty.call(value, k)) {
235 v = walk(value, k);
236 if (v !== undefined) {
237 value[k] = v;
238 } else {
239 delete value[k]
240 }
241 }
242 }
243 }
244 // 处理对象
245 return reviver.call(holder, key, value);
246 }({ ‘‘: result }, ‘‘) : result;
247 }
248 }();
249 // \n是一个字符，\\n是两个字符
250 const str = ‘{"name":"饮料","price":2.5,"cool":true,"description":["雪碧","可乐"],"escapseSlash":"\\/","escapeN":"\\n"}‘;
251 console.log(json_parse(str, (key, val) => val))
252 </script>
253 </body>
254
255 </html>
运行结果
原文地址：https://www.cnblogs.com/sea-breeze/p/11747206.html
时间： 2024-10-10 04:16:15