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• 描述
• 构造函数
• 实例方法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

布尔 对象是用于布尔值的对象包裹器。

描述

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 . All other values, including any object, an empty array ( [] ), or the string " false ", create an object with an initial value of true .

不要混淆 primitive 布尔 值 true and false with the true and false values of the 布尔 对象。

Any object of which the value is not undefined or null , including a 布尔 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 布尔 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 布尔 object to convert a non-boolean value to a boolean value. To perform this task, instead, use 布尔 as a function, or a double NOT operator :

var x = Boolean(expression);     // use this...
var x = !!(expression);          // ...or this
var x = new Boolean(expression); // don't use this!
					

If you specify any object, including a 布尔 object whose value is false , as the initial value of a 布尔 object, the new 布尔 object has a value of true .

var myFalse = new 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 布尔 object in place of a 布尔 primitive.

注意： When the non-standard property document.all is used as an argument for this constructor, the result is a 布尔 object with the value false . This property is legacy and non-standard and should not be used.

构造函数

Boolean()

创建新的 布尔 对象。

实例方法

Boolean.prototype.toString()

Returns a string of either true or false depending upon the value of the object. Overrides the Object.prototype.toString() 方法。

Boolean.prototype.valueOf()

Returns the primitive value of the 布尔 object. Overrides the Object.prototype.valueOf() 方法。

范例

采用 false 初始值创建布尔对象

var bNoParam = new Boolean();
var bZero = new Boolean(0);
var bNull = new Boolean(null);
var bEmptyString = new Boolean('');
var bfalse = new Boolean(false);
					

创建 布尔 对象采用初始值 true

var btrue = new Boolean(true);
var btrueString = new Boolean('true');
var bfalseString = new Boolean('false');
var bSuLin = new Boolean('Su Lin');
var bArrayProto = new Boolean([]);
var bObjProto = new Boolean({});
					

规范

规范
ECMAScript (ECMA-262) The definition of 'Boolean' in that specification.

浏览器兼容性

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request. 更新 GitHub 上的兼容性数据

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
布尔	Chrome 1	Edge 12	Firefox 1	IE 3	Opera 3	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs 0.1.100
Boolean() 构造函数	Chrome 1	Edge 12	Firefox 1	IE 3	Opera 4	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs 0.1.100
toSource 非标	Chrome No	Edge No	Firefox 1 — 74 1 — 74 Starting in Firefox 74, toSource() is no longer available for use by web content. It is still allowed for internal and privileged code.	IE No	Opera No	Safari No	WebView Android No	Chrome Android No	Firefox Android 4	Opera Android No	Safari iOS No	Samsung Internet Android No	nodejs No
toString	Chrome 1	Edge 12	Firefox 1	IE 3	Opera 4	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs 0.1.100
valueOf	Chrome 1	Edge 12	Firefox 1	IE 4	Opera 4	Safari 1	WebView Android 1	Chrome Android 18	Firefox Android 4	Opera Android 10.1	Safari iOS 1	Samsung Internet Android 1.0	nodejs 0.1.100

图例

完整支持

完整支持

不支持

不支持

非标。预期跨浏览器支持较差。

见实现注意事项。

另请参阅

• 布尔
• Boolean 原语
• 布尔数据类型 (维基百科)

元数据

• 最后修改： Aug 4, 2020

相关话题

1. 标准内置对象
2. 布尔
3. 方法
   1. Boolean.prototype.toSource()
   2. Boolean.prototype.toString()
   3. Boolean.prototype.valueOf()
4. 继承：
5. Function
6. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
7. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
8. Object
9. 特性
   1. Object.prototype.__proto__
   2. Object.prototype.constructor
10. 方法
    1. Object.prototype.__defineGetter__()
    2. Object.prototype.__defineSetter__()
    3. Object.prototype.__lookupGetter__()
    4. Object.prototype.__lookupSetter__()
    5. Object.prototype.hasOwnProperty()
    6. Object.prototype.isPrototypeOf()
    7. Object.prototype.propertyIsEnumerable()
    8. Object.prototype.toLocaleString()
    9. Object.prototype.toSource()
    10. Object.prototype.toString()
    11. Object.prototype.valueOf()
    12. Object.setPrototypeOf()