How can I parse a .frd file with Javascript?

A .frd file is a type of multi-column numeric data table used for storing information about the frequency response of speakers. A .frd file looks something like this when opened in a text editor:

2210.4492       89.1    -157.7
2216.3086       88.99   -157.7
2222.168        88.88   -157.6
2228.0273       88.77   -157.4

Using javascript, is there a way that I can parse this data in order to return each column separately?

For example, from the .frd file above, I would need to return the values like so:

var column1 = [2210.4492, 2216.3086, 2222.168, 2228.0273];

var column2 = [89.1, 88.99, 88.88, 88.77];

var column3 = [-157.7, -157.7, -157.6, -157.4];

I'm not exactly sure where to begin in trying to achieve this, so any step in the right direction would be helpful!

Solution

I found the following description of the FRD file format and I will follow it.

Let's assume that the content of your .frd file is in the variable called content (the following example is for Node.js):

const fs = require('fs');
const content = fs.readFileSync('./input.frd').toString();

Now if content has your FRD data, it means it's a set of lines, each line contains exactly three numbers: a frequency (Hz), a level (dB), and a phase (degrees). To split your content into lines, we can just literally split it:

const lines = content.split(/\r?\n/);

(normally, splitting just by '\n' would've worked, but let's explicitly support Windows-style line breaks \r\n just in case. The /\r?\n/ is a regular expression that says "maybe \r, then \n")

To parse each line into three numbers, we can do this:

const values = line.split(/\s+/);

If the file can contain empty lines, it may make sense to double check that the line has exactly three values:

if (values.length !== 3) {
  // skip this line
}

Given that we have three values in values, as strings, we can assign the corresponding variables:

const [frequency, level, phase] = values.map(value => Number(value));

(.map converts all the values in values from strings to Number - let's do this to make sure we store the correct type).

Now putting all those pieces together:

const fs = require('fs');
const content = fs.readFileSync('./input.frd').toString();

const frequencies = [];
const levels = [];
const phases = [];

const lines = content.split(/\r?\n/);
for (const line of lines) {
  const values = line.split(/\s+/);
  if (values.length !== 3) {
    continue;
  }
  const [frequency, level, phase] = values.map(value => Number(value));
  frequencies.push(frequency);
  levels.push(level);
  phases.push(phase);
}

console.log(frequencies);
console.log(levels);
console.log(phases);

The main code (the one that works with content) will also work in browser, not just in Node.js, if you need that.

This code can be written in a tons of different ways, but I tried to make it easier to explain so did something very straightforward.

To use it in Node.js (if your JavaScript file is called index.js):

$ cat input.frd 
2210.4492       89.1    -157.7
2216.3086       88.99   -157.7
2222.168        88.88   -157.6
2228.0273       88.77   -157.4

$ node index.js 
[ 2210.4492, 2216.3086, 2222.168, 2228.0273 ]
[ 89.1, 88.99, 88.88, 88.77 ]
[ -157.7, -157.7, -157.6, -157.4 ]