Question

I’ve read a lot about Data Types in javascript, but found nothing about long int.
I need to know how to define Long Int in javascript.
The reason is the input of following methods of Range object accepts Long data type as second parameter :

    var storedSelection = document.createRange();
    storedSelection.setStart(document.body,  );
    storedSelection.setEnd(document.body,  );

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Answer 1

If you’ve read a lot about JavaScript’s data types as you say then you should already know that:

1. JS variables are loosely typed. That is, when you declare a variable you don’t give it a type (only assigned values have a type).
2. Any given variable can be assigned values of different types at different times. That is, having set x = 12 you can later set x = "some string" or x = { some : "object" } and so forth.
3. JS only has one number type, floating point numbers (IEEE-754 doubles), so generally speaking no distinction is made between integers and decimals.

I don’t know where you read that the range methods accept a “long int data type” as a parameter, but for that parameter you can pass in a JS variable that you know holds an integer, or a numeric literal, or even a function call that returns a number:

function getNumber() {
   return 15;
}

var myVariable = 20;

var storedSelection = document.createRange();
storedSelection.setStart(document.body, 12);
storedSelection.setEnd(document.body, myVariable);
storedSelection.setEnd(document.body, getNumber() );

Further reading: https://developer.mozilla.org/en/JavaScript/Guide/Values,_Variables,_and_Literals

P.S. If you have a non-integer value as a result of a calculation, say you’re calculating your range by dividing the total length by three or something, you can force the result to be an integer by rounding to the nearest integer with Math.round() or rounding down with Math.floor() or rounding up with Math.ceil(). See also the Math object.