Hey, let's break down and fix your issue step by step!

First, let's understand the two problems in your code #

1. Logical error in the map function #

Object.keys(items) returns an array of the object's key names, not the values. For your items object, this array would be ["id", "name", "currency"]. When you use index.name in the map callback, you're trying to access a name property on a string (like "id"), which doesn't exist. That's not what you want here.

2. The "cannot convert undefined or null to object" error #

This happens because Object.keys() requires a valid object as input. If your items variable ever becomes null or undefined when this code runs, calling Object.keys(items) will throw this exact error.

Fixes to resolve both issues #

Option 1: Get all property values correctly #

If your goal is to extract all values from the items object, use either of these approaches:

Using Object.values() (simplest way)

const result = Object.values(items);
console.log(result); // Output: [1, "name1", "usd"]

Using Object.keys() with proper value access

If you need to work with the key names while getting values:

const result = Object.keys(items).map(key => items[key]);
console.log(result); // Output: [1, "name1", "usd"]

Option 2: Prevent null/undefined errors #

To avoid the conversion error entirely, add a check to ensure items is a valid object before processing it:

// Safely handle cases where items might be null/undefined
const safeItems = items ?? {}; // Fallback to empty object if items is null/undefined
const result = Object.keys(safeItems).map(key => safeItems[key]);
console.log(result);

Or with a type check for extra safety:

const result = typeof items === 'object' && items !== null
  ? Object.keys(items).map(key => items[key])
  : []; // Return empty array if items is invalid
console.log(result);

Bonus: Iterate over key-value pairs #

If you need both keys and values, use Object.entries():

const result = Object.entries(items).map(([key, value]) => ({ key, value }));
console.log(result);
// Output: [{key: "id", value: 1}, {key: "name", value: "name1"}, {key: "currency", value: "usd"}]

内容的提问来源于stack exchange，提问作者saon