Boolean() constructor
The Boolean()
constructor can create Boolean
objects or return primitive values of type boolean.
Try it
Syntax
new Boolean(value)
Boolean(value)
Note: Boolean()
can be called with or without new
, but with different effects. See Return value.
Parameters
value
-
The initial value of the
Boolean
object.
Return value
Examples
Creating Boolean objects with an initial value of false
const bZero = new Boolean(0);
const bNull = new Boolean(null);
const bEmptyString = new Boolean('');
const bfalse = new Boolean(false);
typeof bfalse // "object"
Boolean(bfalse) // true
Note how converting a Boolean
object to a primitive with Boolean()
always yields true
, even if the object holds a value of false
. You are therefore always advised to avoid constructing Boolean
wrapper objects.
If you need to take the primitive value out from the wrapper object, instead of using the Boolean()
function, use the object's valueOf()
method instead.
const bfalse = new Boolean(false);
bfalse.valueOf() // false
Creating Boolean
objects with an initial value of true
const btrue = new Boolean(true);
const btrueString = new Boolean('true');
const bfalseString = new Boolean('false');
const bSuLin = new Boolean('Su Lin');
const bArrayProto = new Boolean([]);
const bObjProto = new Boolean({});
Specifications
Specification |
---|
ECMAScript Language Specification # sec-boolean-constructor |
Browser compatibility
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