这是我的第一个问题.我试图找到一个答案,但不能老实说,弄清楚我应该使用哪些术语,如果以前有人问过,那么抱歉.
在这里：
我在.txt文件中有数千条记录,格式如下：
(1,3,2,1,'John (Finances)'),(2,7,'Mary Jane'),(3,'Gerald (Janitor),Broflowski'),
… 等等.第一个值是PK,其他3个是外键,第5个是一个字符串.
我需要在Javascript中解析为JSON(或某些东西),但是我遇到麻烦,因为一些字符串带有括号逗号(在第三个记录“Janitor”,例如),所以我不能使用substring …也许修剪正确的部分,但我想知道是否有更聪明的方式来解析它.
任何帮助将非常感激.
谢谢！
解决方法
你不能(读大概不应该)使用正则表达式为此.如果括号中包含另外一个或另一对不匹配,该怎么办？
好消息是,您可以轻松构建一个tokenizer /解析器.
这个想法是跟踪你当前的状态并采取相应的行动.
这里是我刚才在这里写的解析器的草图,重点是向大家展示一般的想法.如果您有任何概念性问题,请告诉我们.
它工作demo here,但我要求你不要在生产中使用它,然后才能理解和修补它.
怎么运行的
那么,我们如何构建解析器呢？
var State = { // remember which state the parser is at.
BeforeRecord:0,// at the (
DuringInts:1,// at one of the integers
DuringString:2,// reading the name string
AfterRecord:3 // after the )
};
var records = []; // to contain the results var state = State.BeforeRecord;
现在,我们迭代字符串,继续进行并读取下一个字符
for(var i = 0;i < input.length; i++){
if(state === State.BeforeRecord){
// handle logic when in (
}
...
if(state === State.AfterRecord){
// handle that state
}
}
现在,剩下的就是在每个状态下将它消耗到对象中：
>如果它在(我们开始解析和跳过任何空白
>读取所有的整数和沟槽,
>四个整数之后,读取字符串从’到下一个’到达它的结尾
>字符串后,读取直到),存储对象,并重新开始循环.
实施也不是很困难.
解析器
var State = { // keep track of the state
BeforeRecord:0,DuringInts:1,DuringString:2,AfterRecord:3
};
var records = []; // to contain the results
var state = State.BeforeRecord;
var input = " (1," // sample input
var workingRecord = {}; // what we're reading into.
for(var i = 0;i < input.length; i++){
var token = input[i]; // read the current input
if(state === State.BeforeRecord){ // before reading a record
if(token === ' ') continue; // ignore whitespaces between records
if(token === '('){ state = State.DuringInts; continue; }
throw new Error("Expected ( before new record");
}
if(state === State.DuringInts){
if(token === ' ') continue; // ignore whitespace
for(var j = 0; j < 4; j++){
if(token === ' ') {token = input[++i]; j--; continue;} // ignore whitespace
var curNum = '';
while(token != ","){
if(!/[0-9]/.test(token)) throw new Error("Expected number,got " + token);
curNum += token;
token = input[++i]; // get the next token
}
workingRecord[j] = Number(curNum); // set the data on the record
token = input[++i]; // remove the comma
}
state = State.DuringString;
continue; // progress the loop
}
if(state === State.DuringString){
if(token === ' ') continue; // skip whitespace
if(token === "'"){
var str = "";
token = input[++i];
var lenGuard = 1000;
while(token !== "'"){
str+=token;
if(lenGuard-- === 0) throw new Error("Error,string length bounded by 1000");
token = input[++i];
}
workingRecord.str = str;
token = input[++i]; // remove )
state = State.AfterRecord;
continue;
}
}
if(state === State.AfterRecord){
if(token === ' ') continue; // ignore whitespace
if(token === ',') { // got the "," between records
state = State.BeforeRecord;
records.push(workingRecord);
workingRecord = {}; // new record;
continue;
}
throw new Error("Invalid token found " + token);
}
}
console.log(records); // logs [Object,Object,Object]
// each object has four numbers and a string,for example
// records[0][0] is 1,records[0][1] is 3 and so on,// records[0].str is "John (Finances)"
