default value of number in typescript

After I read your response, I see that it would have more downsides than benefits. compiler typescript

What is the reasoning for changing that behaviour? There are 5 primitive types (string, number, boolean, undefined, symbol) and two non-primitives (object, function) that are available in user land. That is incorrect JavaScript is a weakly typed language, not un-typed language. In case a non-numeric argument is passed as an argument to the Numbers constructor, it returns NaN (NotaNumber), The following table lists a set of properties of the Number object . How so? A negative precision will throw an error. On compiling, it will generate the following JavaScript code , The Number object contains only the default methods that are a part of every object's definition. Formats a number with a specific number of digits to the right of the decimal. In addition to JavaScript, TypeScript borrows from Java, C#, others. The largest possible value a number in JavaScript can have 1.7976931348623157E+308. Defines how many total digits (including digits to the left and right of the decimal) to display of a number. Well, I had to test if this value was undefined or not. Sign in TypeScript doesn't change the runtime behavior of JavaScript code. And, in this way, it would be more explicit for the developers too. Code that wrote itself would be useful. counter : number = 0, b :boolean= false)? Some of the commonly used methods are listed below . OK, I guess my point was that when you assign a number to a variable the variable changes type from undefined to number, rather than already being a number that can somehow hold undefined. It is an error to try and set it to undefined. It's a number for instance. It's not "crazy" like a madman, but it's not something we do as a language. Well occasionally send you account related emails. Primitive types are passed into functions by value, while non-primitives are passed by reference. By default, this is the Number object. Yeah, I understand you. In my opinion, as I had setted the type number to the parameter, I thought it would be useful if I hadn't had the obligation to check that. to your account. useful in this sense, is very much an opinion. That is either solved by using default arguments (part of ECMAScript) or strict null checks (part of TypeScript). TypeScript like JavaScript supports numeric values as Number objects. Instead, use the behavior of JavaScript and the intentions of program authors as a guide for what makes the most sense in the language. Learn more. I had the opposite reaction.

Returns the function that created this object's instance. counter: number == NaN, b: boolean == undefined). typescript nullable Why would you expect it to be undefined? Have a question about this project? Changing the default behaviour of an established language that is an extension of another language isn't useful, it is crazy. When I've commented for the first time, I had faced the following situation: I had a function that accepted a number as a parameter. A static property of the Number object. You're being more explicit about the type of the variable. // Object is possibly undefined, forced to check. The typeof operator in JavaScript explicitly informs you of what the type of a variable is (hint is in the name of the operator). Would it make sense to add this behavior at compile time, or maybe add a compiler setting to set appropriate default values (e.g. We make use of cookies to improve our user experience. On compiling, it will generate the same code in JavaScript. Auto-magically assigning values to variables has a performance and memory impact on the run-time code.

The function is passed the radix, an integer between 2 and 36 specifying the base to use for representing numeric values. Why would it be "crazy" to want a compiler switch to set default primitive values consistent with those other languages? The Number class acts as a wrapper and enables manipulation of numeric literals as they were objects. If a TypeScript user wants a variable to be initialised, they should initialise the variable. Initial value of Array.reduce method must not accept undefined as T. Exactly mimic the design of existing languages. Given that the primitive types have to hold some value, it is not surprising to assign a default value automatically. It is surprising for an uninitialised variable to have a value other than undefined because that is the behaviour of JavaScript. This doesn't change the default behaviour of JavaScript because JS doesn't have the concept of a primitive type. Forces a number to display in exponential notation, even if the number is in the range in which JavaScript normally uses standard notation. Returns the string representation of the number's value. This doesn't change the default behaviour of JavaScript because JS doesn't have the concept of a primitive type. The text was updated successfully, but these errors were encountered: I think that would be surprising behaviour to anyone who as worked with JavaScript as defined variables without a value are set to undefined. TypeScript is about developer being more explicit about their code, not less.

If TypeScript requires that a boolean type be set to something (and it does), it can figure out that if it is not specified it should be set to false. By clicking Sign up for GitHub, you agree to our terms of service and Returns a string value version of the current number in a format that may vary according to a browser's local settings. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. The primitive cannot hold undefined. Use the prototype property to assign new properties and methods to the Number object in the current document. Statically typed languages typically set primitives to a default value unless explicitly set. Working through some code samples while getting familiar with typescript, and have noticed that typescript doesn't assign default values to primitive types(e.g. A number object converts numeric literal to an instance of the number class. You signed in with another tab or window. Given that the primitive types have to hold some value, it is not surprising to assign a default value automatically. The smallest possible value a number in JavaScript can have 5E-324. privacy statement. Agree When I declare a variable as a number, I'd prefer its value to be 0, not undefined.

Not a big deal, I can certainly adjust. Already on GitHub? In my opinion, as I had setted the type number to the parameter, I thought it would be useful if I hadn't had the obligation to check that. By using this website, you agree with our Cookies Policy. Well, I had to test if this value was undefined or not. I don't really know if it's been planning to implement this, but I think it'd be very useful. Once you've established that it makes sense to initialize it to a default value (which is why most other languages do it).

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