What steps can I take to avoid unintentionally populating this object with undefined values?

This issue occurs when the variable level is initialized with the value 'undefined'.

Although this code functions correctly in JavaScript, it encounters problems when using TypeScript.

interface Find {
    level?: string;
}

let find: Find = {};

if (!!level) {
     find.level = level;
}

The final value of the object 'find' will be:

{"level":"undefined"}

Instead of just:

{}

Answer №1

The current value is:

{"level":"undefined"}

If it were undefined it would display as:

{"level":undefined}

But what you actually have is the string "undefined".

Solution

interface Find {
    level?: string;
}

let find: Find = {};

if (!!level && level !== "undefined") {
     find.level = level;
}

Now you will see {}.

Additional Info

TypeScript does not impact JavaScript runtime behavior.

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