Optional properties in object literals

[daniel.rentz]

Optional keys in objects

I have typical problem with javascript. Say, I have an input object, which, in some cases, could be enrich with additional keys. I have two options how to do that. First: function enrich(input, optionalData) { return { ...input, additionalKey: optionalData } } Now I could have an object with { additionalKey: undefined }, which could lead to bugs. For example, additionalKey will be lost after JSON.stringify/parse. Another bug: check key with operator in ('additionalKey' in obj), whi…