Declaring a boolean in JavaScript using just var

Question

If I declare a JavaScript boolean variable like this:

var IsLoggedIn; 

And then initialize it with either true or 1, is that safe? Or will initializing it with 1 make the variable a number?

Answer 1

Types are dependent to your initialization:

var IsLoggedIn1 = "true"; //string var IsLoggedIn2 = 1; //integer var IsLoggedIn3 = true; //bool 

But take a look at this example:

var IsLoggedIn1 = "true"; //string IsLoggedIn1 = true; //now your variable is a boolean 

Your variables' type depends on the assigned value in JavaScript.

Answer 2

No it is not safe. You could later do var IsLoggedIn = "Foo"; and JavaScript will not throw an error.

It is possible to do

var IsLoggedIn = new Boolean(false); var IsLoggedIn = new Boolean(true); 

You can also pass the non boolean variable into the new Boolean() and it will make IsLoggedIn boolean.

var IsLoggedIn = new Boolean(0); // false var IsLoggedIn = new Boolean(NaN); // false var IsLoggedIn = new Boolean("Foo"); // true var IsLoggedIn = new Boolean(1); // true