O objeto Boolean
é um wrapper objeto para um valor booliano.
Sintaxe
new Boolean([value])
Parâmetros
value
- Opcional. O valor incial do objeto
Boolean
.
Descrição
The value passed as the first parameter is converted to a boolean value, if necessary. If the value is omitted or is 0
, -0
, null
, false
, NaN
, undefined
, or the empty string (""
), the object has an initial value of false
. If the DOM object document.all
is passed as a parameter, the new boolean object also has an initial value of false
. All other values, including any object or the string "false"
, create an object with an initial value of true
.
Do not confuse the primitive Boolean
values true
and false
with the true
and false
values of the Boolean
object.
Any object of which the value is not undefined
or null
, including a Boolean
object whose value is false
, evaluates to true
when passed to a conditional statement. For example, the condition in the following if
statement evaluates to true
:
var x = new Boolean(false);
if (x) {
// this code is executed
}
This behavior does not apply to Boolean
primitives. For example, the condition in the following if
statement evaluates to false
:
var x = false;
if (x) {
// this code is not executed
}
Do not use a Boolean
object to convert a non-boolean value to a boolean value. Instead, use Boolean
as a function to perform this task:
var x = Boolean(expression); // preferred
var x = new Boolean(expression); // don't use
If you specify any object, including a Boolean
object whose value is false
, as the initial value of a Boolean
object, the new Boolean
object has a value of true
.
var myFalse = Boolean(false); // initial value of false
var g = Boolean(myFalse); // initial value of true
var myString = new String('Hello'); // string object
var s = Boolean(myString); // initial value of true
Do not use a Boolean
object in place of a Boolean
primitive.
Propriedades
Boolean.length
- Length property whose value is 1.
Boolean.prototype
- Represents the prototype for the
Boolean
constructor.
Métodos
While the global Boolean
object contains no methods of its own, it does inherit some methods through the prototype chain:
Instâncias Boolean
All Boolean
instances inherit from Boolean.prototype
. As with all constructors, the prototype object dictates instances' inherited properties and methods.
Propridades
Métodos
Exemplos
Criar objetos Boolean
com um valor inicial de false
var bNoParam = Boolean();
var bZero = Boolean(0);
var bNull = Boolean(null);
var bEmptyString = Boolean('');
var bfalse = Boolean(false);
Criar objetos Boolean
com um valor inicial de verdadeiro
var btrue = Boolean(true);
var btrueString = Boolean('true');
var bfalseString = Boolean('false');
var bSuLin = Boolean('Su Lin');
var bArrayProto = Boolean([]);
var bObjProto = Boolean({});
Especificações
Especificação | Estado | Comentário |
---|---|---|
ECMAScript 1st Edition (ECMA-262) | Standard | Initial definition. Implemented in JavaScript 1.0. |
ECMAScript 5.1 (ECMA-262) The definition of 'Boolean' in that specification. |
Standard | |
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Boolean' in that specification. |
Standard | |
ECMAScript (ECMA-262) The definition of 'Boolean' in that specification. |
Living Standard |
Compatibilidade de navegador
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