unrecognised format string "{spec}"; the value will be stringified

Warnings reference › format:*

Identifier

format:*

Raised by

The grid (core)

Since

1.0.1

What happened

A format given as a string matched neither the shorthand forms nor anything that reads as a date pattern, so no formatter was compiled. Values render as their plain string form - unrounded, unlocalised, no currency or unit.

The fix

Use one of the shorthands, a date pattern, or a format spec object.

The smallest fix

columns: [{ id: 'amount', format: { style: 'currency', currency: 'GBP' } }]

Reference

Covered in full at the API reference.