Applying the spread operator in the map function for copying objects

In my Angular application, I am attempting to copy an object and add a new property using the spread operator. To add the new property, I have created a method called 'addNewProperty(name)' which returns the property and its value. However, when I try to call this method using the spread operator, I encounter an error mentioning Unexpected token.

Here is the code snippet:

this.files = files['results'].map(file => ({...file, this.addNewProperty(file.name)}));

addNewProperty(name) {
    return {
        extension: name.split('-')[1]
    };
}

Interestingly, when I use the "traditional" Object.assign() method instead, everything works smoothly:

this.files = files['results'].map(file => Object.assign(file, this.addNewProperty(file.name)));

I would appreciate it if someone could explain why Object.assign() functions correctly for copying objects, while trying to achieve the same with {..., myMethod()} does not work as expected.

Answer №1

Ensuring you spread the new object is crucial to avoid missing a key in your data structure.

this.data = data['output'].map(info => ({...info, ...this.updateInfo(info.title)}));
//                                                   ^^^

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