CODEWITHSUNDEEP
javascriptnode.jsregexpattern-matching
Ashish Johnson
Ashish Johnson

Reputation: 467

how to fix TypeError: Cannot read property 'match' of undefined

I'm filtering the text file in nodejs and the "match" regex is giving me error on the filtered array

var fs = require("fs");
var finalarray = [];
var data = [];
var data1 = [];

fs.readFile('dataforparsing', function (err, buf) {

  finalarray = buf.toString();// convert the object into the string

  data = finalarray.split("\n");// splitting based on new line

  for (i = 0; i < data.length; i++) {
    if (data[i].match(/sessionid:/g) && !data[i].match(/Input/g)) {// filtering of the rows
      data1[i] = data[i].toString();
      console.log(data1[i] + "\n");
    }
  }

var data3 = [];

for (i = 0; i < data1.length; i++) {
    data3[i] = data1[i].match(/[0-9]{13}/g);
    console.log(data3[i] + "\n");
  }

});

The expectation is that the code should work in the last loop as well but it gives error at "data1[i].match(..)" and print the filtered output based on the REGEX expression.

Upvotes: 0

Views: 4093

Answers (2)

Shivam Kubde
Shivam Kubde

Reputation: 623

Use Arrays's push method to set data1 array elements.

var fs = require("fs");
var finalarray = [];
var data = [];
var data1 = [];

fs.readFile('dataforparsing', function (err, buf) {

  finalarray = buf.toString();// convert the object into the string

  data = finalarray.split("\n");// splitting based on new line

  for (i = 0; i < data.length; i++) {
    if (data[i].match(/sessionid:/g) && !data[i].match(/Input/g)) {// filtering of the rows
      data1.push(data[i].toString());

    }
  }

var data3 = [];

for (i = 0; i < data1.length; i++) {
    data3[i] = data1[i].match(/[0-9]{13}/g);
    console.log(data3[i] + "\n");
  }

});

Hope this will help.

Upvotes: 1

epascarello
epascarello

Reputation: 207501

The problem is you only fill in indexes where you find matches

if (data[i].match .... ) { data1[i] = data[i].toString(); <-- that i is killing you }

so when you do not have a match you have

data[0] -- match
data[1] -- undefined
data[2] -- match

You want to use push() not set the index

data1.push(data[i]);

But in the end you are just rewriting filter()

var data1 = data.filter(item => item.match(/sessionid:/g) && !item.match(/Input/g))

Upvotes: 1

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