For Loops and Logging Counters in Observable Notebooks

Question

I am trying to loop through an array, and print a counter number for every object in that array. I am starting with the following logic:

{for (let i = 0; i < 10; i++){
   print(i)}
}

In Observable Notebooks (observablehq), this returns "undefined". So, I don't get any print statements. I am hoping to transfer this logic to loop through objects in an array, and count each object. But, I'm stuck with simply trying to use a counter!

I've also tried this:

import {log} from '@sorig/console-log-without-leaving-your-notebook'

{for (let i = 0; i < 10; i++){
   console.log(i)}
}

This also returns 'undefined'.

Answer 1

console.log works fine inside Observable. I'm not sure if was a typo, but print(i) is not a javascript method, did you mean console.log? if you try the below snippet and open developer tools you will see lines printed.

unamedcell = {
  for (let i = 0; i < 10; i++){
    console.log(i);
  }
}

However, remember that inside Observable you have a different flavor of javascript.

Observable’s not JavaScript

It returns undefined because you're not naming the cells.

If I understand your needs, looping through an array of objects there. First name a cell with you data, you could also fetch from somewhere else. Then another cell using that data Here is a fictitious case :

data = {
  // your data
  const myObjects = [
    { a: 10, b: 20 },
    { a: 1, b: 2 },
    { a: 1, b: 5 },
    { a: 2, b: 10 }
  ];
  return myObjects;
}
// data = Array(4) [Object, Object, Object, Object]

then another cell

dataExample = {
  let asum = 0;
  let bsum = 0;
  for (let i = 0; i < data.length; i++) {
    asum += data[i].a;
    bsum += data[i].b;
  }
  return { asum, bsum };
}
// dataExample = Object {asum: 14, bsum: 37}

More info on their user manual