In the following JavaScript code, why does it throw a ReferenceError, and how would you fix it?

The error occurs because array_push is not a built‑in JavaScript function. In JavaScript, arrays have a method called push that adds elements to the end of the array. The correct code should be:

const arr = [];
arr.push('abc');
console.log(arr); // ['abc']

If you need to mimic PHP’s array_push, you can create a helper:

function array_push(arr, ...items) {
  return arr.push(...items);
}

But using the native push is simpler and more idiomatic. The ReferenceError is thrown because the interpreter cannot find a variable or function named array_push in the current scope.