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JavaScript REST APIs with Express Getting to Know REST APIs GET a Quote, GET all Quotes

codingchewie
codingchewie
8,764 Points
Posted by codingchewie
codingchewie
8,764 Points

Why does a strict comparison operator not work here?

After modifying the code from the video to:

app.get('/quotes/:id', (req, res) => res.status(200).json(data.records.find((quote) => quote.id === req.params.id)))

the strict comparison operator will not return anything if I pass http://localhost:3000/quotes/3406 in the browser or in Postman.

When I modify the line to:

app.get('/quotes/:id', (req, res) => res.status(200).json(data.records.find((quote) => quote.id == req.params.id)))

I'm able to get JSON in Postman and the browser. I know this is a stripped down approach but I'm curious why doesn't the strict comparison work here?

Steffeni Veren
Steffeni Veren
7,259 Points
Steffeni Veren
Steffeni Veren
7,259 Points

Are they two different types? Strict compares values AND types where as == will coerce the types and match if they have the same value.

2 Answers

Steven Parker
Steven Parker
231,275 Points
Steven Parker
Steven Parker
231,275 Points

As Steffeni suggested, if one value is a string and the other is a number, the standard comparison will apply conversion for you. The strict comparison operator would consider them to be different no matter what they contain.

Mathew Gries
Mathew Gries
7,072 Points
Mathew Gries
Mathew Gries
7,072 Points

To expand further for anyone that runs into this issue or has this question, check this site https://en.wikibooks.org/wiki/Computer_Programming/Type_conversion

request.params.id is a string type, and the quotes.id is a number type something to watch out for when coding. I have banged my head against the wall a few times because of this.