Introduction to array

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import * as path from 'path';
import { fileURLToPath } from 'url';
import { defineConfig } from 'astro/config';

const __dirname = path.dirname(fileURLToPath(import.meta.url));

// https://astro.build/config
export default defineConfig({
  vite: {
    resolve: {
      alias: [{ find: '@', replacement: path.resolve(__dirname, 'src') }],
    },
  },
});

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Ex: Get the last item of an array

Write a function last(arr) that returns the last element of an array.

For examples,

last([1, 2, 3]); // 3
last([]); // undefined

function last(arr) {
  // @TODO
}

assert(last([]), undefined);
assert(last([1, 2, 3]), 3);
assert(last(['foo', 'bar']), 'bar');

Hint

You should do this and that. Can read this to understand more.

But don’t do this.

Because this is not so good

Definitely not this

console.log(1);

Solution

function last(arr) {
  return arr[arr.length - 1];
}

Ex: Count number of items in an array

Write a function count(arr) that returns the number of items in an array.

For examples,

count(['a']); // 1
count(['a', 2, nul]); // 3
count([]); // 0

function count(arr) {
  // @TODO
}

assert(count(['a']), 1);
assert(count(['a', 2, nul]), 3);
assert(count([]), 0);

Hint

You can use .length. Or write a simple function.

Solution

function count(arr) {
  let counter = 0;

  for (const el of arr) {
    counter = counter + 1;
  }

  return counter;
}

function count(arr) {
  return arr.length;
}