I am try to filter objects depending on if they have a certain property.

Example:

objectArray = [{a: "", b: ""}, {a: ""}]
objectArray.filter( obj => "b" in obj ).forEach(obj => console.log(**obj.b**))

typescript complains about the obj.b, since some objects doesn't have the b property, but since I filter them out it shouldn't. What am I doing/getting wrong.

CodePudding user response：

Declare objectArray in the same statement where it is initialized (with let or const). This will allow TypeScript to infer the type of the expression objectArray.filter( obj => "b" in obj ) correctly, i.e.

const objectArray = [{a: "", b: ""}, {a: ""}];
objectArray.filter( obj => "b" in obj ).forEach(obj => console.log(obj.b)); // no error

Playground link

CodePudding user response：

Objects.keys can help you

objectArray.filter(x=> Object.keys(x).indexOf('b')>=0 );