Question

我正在node js采取婴儿步骤。第一项任务，逐行读取分隔文件，并吐出包含字符串“imputed”的行。

#!/usr/bin/env node

var Csv = require("csv"),
    Fs = require("fs");

var foods = "/../data/sr26";


    Csv()
        .from.stream(
            Fs.createReadStream(__dirname + foods + "/SRC_CD.txt"),
            {"delimiter": "^", "quote": "~"}
        )
        .to(function(data, count) {
            console.log(data);
        })
        .transform(function(row, index, callback) {
            //if (row[1].search(/imputed/) != -1) {
                process.nextTick(function() {
                     callback(
                        null, 
                        row[1].substr(0, 15) + "… " + row[1].search(/imputed/) + "\n"
                    )
                });
            //}
        });

打印

Analytical or d… -1
Calculated or i… 14
Value manufactu… -1
Aggregated data… -1
Assumed zero… -1
Calculated from… -1
Calculated by m… -1
Aggregated data… -1
Manufacturer's … -1
Analytical data… -1

但取消注释transform内的比较会导致根本没有输出。我做错了什么？

Answer 1

异步使用csv transform method时，必须调用回调。
如果使用null调用它，则只会跳过该记录。

if (row[1].search(/imputed/) != -1) {

  process.nextTick(function() {
    callback(
      null, 
      row[1].substr(0, 15) + "… " + row[1].search(/imputed/) + "\n"
    )
  });

} else {
  callback(null, null);
}

用CSV中的节点js写出匹配的行

1 个答案: