Node.js内置模块readline在关闭后保持读取行

Question

我有以下代码：

const fs = require("fs");
const {createInterface} = require("readline");
const {join} = require("path");
const {once} = require("events");
async function readMeta (path) {
const meta = {};
const rs = fs.createReadStream(path);
const lineReader = createInterface({input: rs});
let linesRead = 0;
lineReader.on("line", line => {
switch (linesRead) {
case 0:
meta.name = line;
break;
case 1:
meta.tags = line.split(" ");
break;
case 2:
meta.type = line;
break;
case 3:
meta.id = +line;
}
if (++linesRead === 4) {
lineReader.close();
}
});
await once(lineReader, "close");
rs.close();
return meta;
}

它似乎在工作，但在line事件触发时记录行显示情况并非如此。调用lineReader.close()导致读取整个文件后，事件仍在激发。我不知道是什么原因造成的。我发现一些模块显然可以完成这项工作，但如果可能的话，我想降低依赖关系。

Answer 1

我建议不要处理和切换计数器，而是将行推送到数组，并在数组大小为4后防止进一步推送。

然后调用close和after，将数组销毁为必要的属性并返回包含这些属性的对象。

const fs = require("fs");
const {createInterface} = require("readline");
const {join} = require("path");
const {once} = require("events");
async function readMeta (path) {
const meta = {};
const rs = fs.createReadStream(path);
const lineReader = createInterface({input: rs});
const linesRead = [];
lineReader.on("line", line => {
if (linesRead.length === 4) {
lineReader.close();
rs.close();
return;
}
linesRead.push(line.trim());
});
await once(lineReader, "close");
delete rs;
delete lineReader;
const [name, tags, type, id] = linesRead;
return {
id,
name,
type,
tags: tags.split(' '),
};
}