Spot the bug in the order formatter

Node 24 beginner 4 min 1 issue to find

Find why this generated formatter throws when map invokes it.

JavaScript

'use strict';

const formatter = {
  prefix: 'ORD',
  format(id) {
    return `${this.prefix}-${id}`;
  },
};

console.log(['7', '8'].map(formatter.format));

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