how to add field to array object in javascript code example

Example: javascript add field to array

//you can add custom properties to the JS arrays
  //length won't change
  
  const arr = [ 1, 2, 3, 4 ];
  arr.greeting = 'Hello, world!';

  console.log(arr.length); // 4
  console.log(arr.greeting); // Hello, world!