Type checking when code is running

I am using TypeScript on Node.js. TypeScript checks types during compilation, but JavaScript code after compiling is not checking types. For example, this code throws an error:

var test : number;
test = 'test';

But this code on Express will work normally:

app.post('/', function(req, res, next) {
    var test : number;
    test = req.body.test;
    res.end(req.body.test);
});

As a result, I have test with string type, although test was a number. How can I avoid this problem? How do I check the type of variables when code is running?

Answers


How do I check the type of variables when code is running

Basically TypeScript is inferring the type of req to be any. This means it it as completely not type checked to a large extent.

You can disable this with noImplicitAny option and then TypeScript will flag errors when it cannot determine the type of a variable. That would make your code sample a compile time error.


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