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📜  TypeScript-数字

📅  最后修改于: 2020-10-19 03:52:24             🧑  作者: Mango

像JavaScript的TypeScript支持将数值作为Number对象。数字对象将数字字面量转换为数字类的实例。 Number类充当包装器，并允许对数字字面量进行操作，因为它们是对象。

句法

var var_name = new Number(value)

如果将非数字参数作为参数传递给Number的构造函数，则它将返回NaN（Not–a–Number）

下表列出了Number对象的一组属性-

S.No. Property & Description
1.

MAX_VALUE

The largest possible value a number in JavaScript can have 1.7976931348623157E+308.
2.

MIN_VALUE

The smallest possible value a number in JavaScript can have 5E-324.
3.

NaN

Equal to a value that is not a number.
4.

NEGATIVE_INFINITY

A value that is less than MIN_VALUE.
5.

POSITIVE_INFINITY

A value that is greater than MAX_VALUE.
6.

prototype

A static property of the Number object. Use the prototype property to assign new properties and methods to the Number object in the current document.
7.

constructor

Returns the function that created this object’s instance. By default, this is the Number object.

例

console.log("TypeScript Number Properties: "); 
console.log("Maximum value that a number variable can hold: " + Number.MAX_VALUE); 
console.log("The least value that a number variable can hold: " + Number.MIN_VALUE); 
console.log("Value of Negative Infinity: " + Number.NEGATIVE_INFINITY); 
console.log("Value of Negative Infinity:" + Number.POSITIVE_INFINITY);

编译时，它将在JavaScript中生成相同的代码。

其输出如下-

TypeScript Number Properties:  
Maximum value that a number variable can hold: 1.7976931348623157e+308 
The least value that a number variable can hold: 5e-324 
Value of Negative Infinity: -Infinity 
Value of Negative Infinity:Infinity

示例：NaN

var month = 0 
if( month<=0 || month >12) { 
   month = Number.NaN 
   console.log("Month is "+ month) 
} else { 
   console.log("Value Accepted..") 
}

编译时，它将在JavaScript中生成相同的代码。

其输出如下-

Month is NaN

示例：原型

function employee(id:number,name:string) { 
   this.id = id 
   this.name = name 
} 

var emp = new employee(123,"Smith") 
employee.prototype.email = "smith@abc.com" 

console.log("Employee 's Id: "+emp.id) 
console.log("Employee's name: "+emp.name) 
console.log("Employee's Email ID: "+emp.email)

编译时，它将生成以下JavaScript代码-

//Generated by typescript 1.8.10
function employee(id, name) {
   this.id = id;
   this.name = name;
}

var emp = new employee(123, "Smith");
employee.prototype.email = "smith@abc.com";

console.log("Employee 's Id: " + emp.id);
console.log("Employee's name: " + emp.name);
console.log("Employee's Email ID: " + emp.email);

其输出如下-

Employee’s Id: 123 
Emaployee’s name: Smith 
Employee’s Email ID: smith@abc.com

编号方法

Number对象仅包含默认方法，这些方法是每个对象定义的一部分。下面列出了一些常用的方法-

S.No. Methods & Description
1. toExponential()

Forces a number to display in exponential notation, even if the number is in the range in which JavaScript normally uses standard notation.
2. toFixed()

Formats a number with a specific number of digits to the right of the decimal.
3. toLocaleString()

Returns a string value version of the current number in a format that may vary according to a browser’s local settings.
4. toPrecision()

Defines how many total digits (including digits to the left and right of the decimal) to display of a number. A negative precision will throw an error.
5. toString()

Returns the string representation of the number’s value. The function is passed the radix, an integer between 2 and 36 specifying the base to use for representing numeric values.
6. valueOf()

Returns the number’s primitive value.