What are JavaScript Data Types?
There's
Numbers
Strings
Booleans
Objects
null
undefined
Note that there isn't a separate Integer, just number - which is represented as a double precision floating point number.
There's also
Functions
Arrays
RegExps
all of which are Objects deep down, but with enough special wiring to be mentioned on their own.
There are five primitive data types in JavaScript:
number
string
boolean
undefined
null
Everything that is not a primitive is an object.
Javascript has a typeof operator that returns a string that names the datatype of its argument. So, you could say that the datatypes in Javascript are all the possible return values of this operator. Look here:
https://developer.mozilla.org/en/JavaScript/Reference/Operators/typeof
Related
I thought that BigInt method and any number postfix n convention method are the same. Am I wrong? The issue explained below:
Firstly, I have summed two numbers i.e.
a = 812409329480932850928309582n;
b = 382759230958092895809328955n;
using any number postfix n convention method.
Secondly, I have summed the same numbers stored in a different variable i.e.
c = BigInt(812409329480932850928309582);
d = BigInt(382759230958092895809328955);
using BigInt method. But, the issue here is that I am getting different answers as shown in the picture. Can someone help me out here?
The parameters passed by your code to the BigInt() constructor are plain numbers, and they're beyond the range of safely-representable integers. Thus those constants are imprecise as numbers, and your resulting BigInt values are incorrect.
Using the constant syntax is the way to do it if you have the actual constant values (strings of digits).
If you really want to use the constructor, you can pass the values in as strings instead of numeric constants. The constructor will correctly parse the strings as BigInt constants.
The MDN page on Array#slice states:
For strings, numbers and booleans (not String, Number and Boolean
objects), slice copies the values into the new array. Changes to the
string, number or boolean in one array do not affect the other array.
Surely string literals, being reference types (admittedly with a value semantic), are not copied. Instead a reference is copied?
String literals produce immutable primitive values. Those are not reference values.
That strings might be implemented with shared references to character arrays in JS engines is just that, an implementation detail. As you say yourself, strings do have value semantics in JS, and that's all what matters.
No, string literals are considered primitive types in JavaScript, just like numbers.
See MDN - Strings # Distinction between string primitives and String objects
I tried to search here but seems I can't find the best answer to my problem.
How can I validate if the user input is double, Float or Long (data types in JAVA) in javascript?
If you want to check for an object type you can use typeof keyword of javascript. For example if you want to check for a number you can do something like this:
typeof i === 'number'
or using regex for floating types:
^\d{0,2}(\.\d{0,2}){0,1}$
I don't think there is such a difference in javascript.
Does JavaScript have double floating point number precision?
There are not such types in javascript.
The types you said in javascript is a primitive data type called Number.
In JavaScript, all numbers are 64-bit floats. Functions like parseInt() treat their input like a signed int, but create a float. And bit-wise operators recreate the same behaviour you would expect with ints, but on floats.
The Javascript number primitive can't represent the range of values that the combination of Javas int, long and double can. If you really need to validate this anyway you could always write some kind of hack. For example, for the Java long you could:
store javaLongMaxValue as a string,
interpret your input number as a string,
left pad your input string with "0" until it is javaLongMaxValue.length long
and then compare the strings.
You would of course have to validate that the input can be interpreted as a number and handle the case when it's negative.
use if statements and parse it
parseInt('var');
parseDouble('var');
so on..
example..
if(parseInt('var')){
// code above checks if it is a integer.. returns 'true' if yes and 'false' if not
// then your code
}else if(parseDouble('var')){
// your code
}
.. so on
In JavaScript, variables are loosely typed, so the number 5 and the string "5" may both be treated as a number by several operators. However, is there a generic way to find out JavaScripts conversion abilites in at tunrime, or is it just the overloading of operators for several types that make the loose typing possible?
For example, given a variable a and a string containing a type name type_canditate, is there any way to ask JavaScript, if a may convert to type_candidate in a feasable manner, in contrast to the hard typing operators like instanceof? For example, "5" instanceof Number evaluates false, while Math.sin("5") is perfectly feasable. For numbers, one can obviuosly check if parseFloat(some_number) evaluates to NaN, but this is a special case for numbers.
So, is there any generic way of naming types, and check if some variable may convert to a given type in a useful manner?
There are three primitive data types in JavaScript: string, number and boolean.
Anything can be converted to a string or boolean:
All objects convert to true (except null, which becomes false - I only mention it here because typeof null gives object)
All objects have a built-in toString method which is called when converting to a string.
Converting a number to a string is done by giving the string representation of the number (ie. 5 becomes "5")
Numbers convert to boolean true, unless it's 0 which becomes false.
Converting to a number is a little trickier, but technically possible. If it can find a valid number, then it becomes that number. Otherwise, it becomes NaN.
So basically... any type can become any other type through casting in this way. The only time you have anything resembling an "error condition" is NaN.
I have recently seen some references that explain Strings in Javascript as a primitive type.I know that a primitive is a data type that is composed of no other data types and can not be broken down any further.But the problem is I have also read strings are objects.How it can be both ?Please clarify me about the confusion.
You can read about that exact topic on MDN:
Note that JavaScript distinguishes between String objects and
primitive string values. (The same is true of booleans and numbers.)
String literals (denoted by double or single quotes) and strings
returned from String calls in a non-constructor context (i.e., without
using the new keyword) are primitive strings. JavaScript automatically
converts primitives to String objects, so that it's possible to use
String object methods for primitive strings. In contexts where a
method is to be invoked on a primitive string or a property lookup
occurs, JavaScript will automatically wrap the string primitive and
call the method or perform the property lookup.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String