jsonx.js

/**
 * 引号内逃逸字
 */
const ESC = '\\';
/**
 * TOKEN状态名称聚合定义
 */
const ST = {
	'"': 'quote',
	"'": 'quote',
	',': 'comma',
	':': 'colon',
	'{': 'nest',
	'[': 'nest',
	'(': 'nest',
};
/**
 * 成对嵌套字符集
 */
const NESTS = { '{': '}', '[': ']', '(': ')' };
/**
 * 检查字符状态
 * @param {String} c 字符
 */
const _st = (c) => c in ST ? ST[c] : 'plain';
/**
 * 去头尾空格
 * @param {String} s 字符串
 */
const trim = s => s.replace(/^\s+|\s+$/g, '');
const LnCol = (str, i) => {
	let lns = str.substr(0, i + 1).split('\n');
	return [lns.length, lns.pop().length];
}
/**
 * 创建一个读取单位节点
 * @param {String} s 原始字符串
 * @param {Number} index 开始索引位置
 * @param {Number} size 字符串长度
 * @param {Object} ext 扩展属性对象
 */
const seg = (s, index, size, ext = {}) => {
	let status = _st(s[index]);
	let text = s.substr(index, size);
	switch(status){
		case 'quote':
			text = text.substr(1, text.length - 2);
			break;
		case 'plain':
			text = trim(text)
			break;
	}
	return { status, text, ...ext };
};
/**
 * 转换节点为JS值
 * @param {Object} n 节点
 */
const value = n => {
	switch(n.status){
		case 'plain':
			return JSON.parse(n.text);
		case  'nest':
			return n.left in parser ? parser[n.left](n) : n.text;
		default:
			return n.text;
	}
};
/**
 * 各TOKEN读取方法
 */
const readers = {
	quote: (s, _i, sub) => {
		let i = _i, len = s.length, q = s[i++], c;
		for(; i < len; i++){
			c = s[i];
			if(c === ESC){
				i += 1;
			} else if(c === q){
				sub.push(seg(s, _i, i - _i + 1, { quote: q }))
				return i;
			}
		}
		let [ln, col] = LnCol(s, _i);
		throw `Quote is not closed. [${q}] at Ln ${ln} Col ${col}`;
	},
	nest: (s, _i, _sub) => {
		let i = _i, left = s[i++], right = NESTS[left], c, st;
		let j = i;
		let sub = [];
		for(; i < s.length; i++){
			c = s[i];
			st = _st(c);
			if(st in readers){
				if(i > j){
					sub.push(seg(s, j, i - j))
				}
				i = readers[st](s, i, sub);
				j = i + 1;
			} else if(c === right){
				if(i > j){
					sub.push(seg(s, j, i - j))
				}
				sub = sub.filter(n => n.status !== 'plain' || !/^\s*$/.test(n.text));
				_sub.push(seg(s, _i, i - _i + 1, { left, sub }));
				return i;
			}
		}
		let [ln, col] = LnCol(s, _i);
		throw `Nest is not closed. "${left}" at Ln ${ln} Col ${col}`;
	},
	comma: (s, i, sub) => {
		sub.push(seg(s, i, 1));
		return i;
	},
	colon: (s, i, sub) => {
		sub.push(seg(s, i, 1));
		return i;
	}
};
/**
 * 读取文档，解析为节点集合。
 * @param {String} s 原始字符串
 * @param {Number} i 起始索引
 * @param {Array} r 节点寄存
 */
const read = (s, i = 0, r = []) => {
	let j = i, len = s.length;
	for(; i < len; i++){
		let c = s[i];
		let st = _st(c);
		if(st in readers){
			if(j < i){
				r.push(seg(s, j, i - j))
			}
			i = readers[st](s, i, r);
			if(i < 0){
				return r;
			}
			j = i + 1;
		}
	}
	if(j < i){
		r.push(seg(s, j, i - j))
	}
	return r;
};
/**
 * 嵌套类型值转换器（数组|对象）
 */
const parser = {
	'[': n => n.sub.filter(n => n.status !== 'comma').map(n => value(n)),
	'{': n => {
		let r = {};
		let i = 0, sub = n.sub.filter(n => n.status !== 'comma'), len = Math.floor(sub.length / 3) * 3;
		for(; i < len; i += 3){
			if(sub[i + 1].status !== 'colon'){
				return r;
			}
			r[sub[i + 0].text] = value(sub[i + 2]);
		}
		return r;
	}
};
/**
 * 转换器
 * @param {String} s 原始字符串
 */
const parse = s => {
	let [$1, $2] = read(s);
	let r;
	if($2 && $2.status === 'nest' && $1.status === 'plain'){ // JSONP
		r = $2.sub[0];
	} else {	// JSON
		r = $1;
	}
	return value(r);
};
module.exports = { parse };