Cannot read properties of undefined (JavaScript)

In short: An attempt was made to access a property of undefined or null.

In more detail: The browser names the property, for example “reading ‘length’”.

In Depth

Possible causes

• Data not loaded yet.
• Wrong name or path.
• Object was not created.

Solutions

1. Use optional chaining (obj?.name).
2. Check the value with console.log.
3. Wait for loaded data (async/await).

See also: JS, TypeScript