If you want to update a piece of an object while creating a new object, then the spread syntax is the way to go.

When you see..., you should just think of flattening the object.

When you see this:

constmetadata={first:"Matt",last:"Crowder"};constupdatedMetadata={...metadata,last:"Jenkins"};

You should just seeupdatedMetadata as such:

constupdatedMetadata={first:"Matt",last:"Crowder",last:"Jenkins"};

Key/value assignments are read from top to bottom, so the last key's value will take priority in setting the value.

And nowupdatedMetadata will have the value of:

{first:"Matt",last:"Jenkins"}

So the spread flattens out the object wherever you place it, so if we had placed the spread metadataafterlast: "Jenkins", then we would get no updates!

constmetadata={first:"Matt",last:"Crowder"};constupdatedMetadata={last:"Jenkins",...metadata};// results inconstupdatedMetadata={last:"Jenkins",first:"Matt",last:"Crowder"};// which gives us nothing

So be careful where you place your spread syntax!