JavaScript returns the original value of the Array object method valueOf()

Definition and Usage

The valueOf() method returns the original value of the Array object.

This primitive value is inherited by all objects derived from the Array object. The

valueOf() method is usually automatically called by JavaScript in the background and does not appear explicitly in the code.

Syntax

arrayObject.valueOf()

The valueOf() function is used to return the original value of the specified object.

This method belongs to Object object. Since all objects "inherit" the object instance of Object, almost all instance objects can use this method.

All major browsers support this function.

Return value

The valueOf() function returns the original value of the specified object.

Many built-in objects in JavaScript have rewritten this function to achieve more suitable functional needs. Therefore, the return value and return value type of the valueOf() method of different types of objects may be different.

Object	Return value
Array	Array instance object.
Boolean	Boolean value.
Date	A time value stored in milliseconds since midnight on January 1, 1970 UTC.
Function	The function itself.
Number	Number value.
Object	The object itself. This is the default setting.
String	String value.

Examples & Instructions

// Array：返回数组对象本身
var array = ["CodePlayer", true, 12, -5];
document.writeln( array.valueOf() === array ); // true

// Date：当前时间距1970年1月1日午夜的毫秒数
var date = new Date(2013, 7, 18, 23, 11, 59, 230);
document.writeln( date.valueOf() ); // 1376838719230

// Number：返回数字值
var num =  15.26540;
document.writeln( num.valueOf() ); // 15.2654

// 布尔：返回布尔值true或false
var bool = true;
document.writeln( bool.valueOf() === bool ); // true
// new一个Boolean对象
var newBool = new Boolean(true);
// valueOf()返回的是true，两者的值相等
document.writeln( newBool.valueOf() == newBool ); // true
// 但是不全等，两者类型不相等，前者是boolean类型，后者是object类型
document.writeln( newBool.valueOf() === newBool ); // false

// Function：返回函数本身
function foo(){ 
}
document.writeln( foo.valueOf() === foo ); // true
var foo2 =  new Function("x", "y", "return x + y;");
document.writeln( foo2.valueOf() === foo2 ); // true

// Object：返回对象本身
var obj = {name: "张三", age: 18};
document.writeln( obj.valueOf() === obj ); // true

// String：返回字符串值
var str = "http://www.365mini.com";
document.writeln( str.valueOf() === str ); // true
// new一个字符串对象
var str2 = new String("http://www.365mini.com");
// 两者的值相等，但不全等，因为类型不同，前者为string类型，后者为object类型
document.writeln( str2.valueOf() === str2 ); // false

The above is the detailed content of JavaScript returns the original value of the Array object method valueOf(). For more information, please follow other related articles on the PHP Chinese website!