typing

I'm trying to use the --strict option on tsc but I ran into the following "weird" case that I don't seem to understand. If I write: function testStrict(input: {query?: {[prop: string]: string}}) { if (input.query) { Object.keys(input.query).forEach(key => { input.query[key]; }) } return input; } the compiler complains about: test.ts(5,9): error TS2532: Object is possibly 'undefined'. (the offending line is input.query[key]; ) What I don't understand is, I have already checked for undefined with the if guard on the first line of the function if (input.query) , so why does the compiler think it

Considere the following code: from typing import Callable, Any TFunc = Callable[..., Any] def get_authenticated_user(): return "John" def require_auth() -> Callable[TFunc, TFunc]: def decorator(func: TFunc) -> TFunc: def wrapper(*args, **kwargs) -> Any: user = get_authenticated_user() if user is None: raise Exception("Don't!") return func(*args, **kwargs) return wrapper return decorator @require_auth() def foo(a: int) -> bool: return bool(a % 2) foo(2) # Type check OK foo("no!") # Type check failing as intended This piece of code is working as intended. Now imagine I want to extend this, and

In Java 8, type inference has been extended to target typing which enables to write: Comparator<String> ascending = comparingInt(String::length); without having to use a type witness ( Comparator.<String> comparingInt ). However the last statement below does not compile. Is there a reason? Is there a workaround? Comparator<String> ascending = comparingInt(String::length); //ok Comparator<String> descending = ascending.reversed(); //ok Comparator<String> descending = reverseOrder(comparingInt(String::length)); //ok Comparator<String> descending = Comparator.<String>comparingInt(String::length)

I've heard this term used with scripting languages such as PHP. What exactly does it mean? Dynamic typing is a definitive characteristic of a language. A short explanation might be: A language has dynamic typing when it does not associate values strictly with a specific type, but it is designed to "decide" what the type of a value should be at runtime, based on how you are attempting to use it. For example, in PHP you can write $count = "5"; // defines a string variable and then go on to say $count = $count * 2; // this is legal and has the obvious result¹ What happened here? For one, the

I have DIV tag with text inside. Is it possible to change the text content in a loop with a typing effect, where it types out, then goes backward deleting the letters and starting all over with a new text? Is this possible with jquery? Just a simple approach: $("[data-typer]").attr("data-typer", function(i, txt) { var $typer = $(this), tot = txt.length, pauseMax = 300, pauseMin = 60, ch = 0; (function typeIt() { if (ch > tot) return; $typer.text(txt.substring(0, ch++)); setTimeout(typeIt, ~~(Math.random() * (pauseMax - pauseMin + 1) + pauseMin)); }()); }); /* PULSATING CARET */ [data-typer]

Let's suppose there's a typing file for library X which includes some interfaces. interface I1 { x: any; } interface I2 { y: { a: I1, b: I1, c: I1 } z: any } In order to work with this library I need pass around an object that is of exactly the same type as I2.y . I can of course create identical interface in my source files: interface MyInterface { a: I1, b: I1, c: I1 } let myVar: MyInterface; but then I get the burden of keeping it up to date with the one from library, moreover it can be very large and result in lot of code duplication. Therefore, is there any way to "extract" the type of