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📜  TypeScript数字

📅  最后修改于: 2021-01-11 12:30:57             🧑  作者: Mango

打字稿编号

与JavaScript一样，TypeScript中的所有数字都存储为浮点值。这些数字值被视为数字数据类型。该数字用于表示整数和浮点值。数字类型将数字字面量转换为数字类的实例。数字类充当包装器，并处理数字字面量，因为它们是对象。 TypeScript还支持Binary(Base 2)，Octal(Base 8)，Decimal(Base 10)和Hexadecimal(Base 16)字面量。

句法

let identifier: number = value;

例

let first: number = 12.0;             // number 
let second: number = 0x37CF;          // hexadecimal
let third: number = 0o377 ;           // octal
let fourth: number = 0b111001;        // binary 

console.log(first);           // 123
console.log(second);          // 14287
console.log(third);           // 255
console.log(fourth);          // 57

数字属性

Number对象具有以下属性集：

SN Property_Name Description
1. MAX_VALUE It returns the largest possible value of a number in JavaScript and can have 1.7976931348623157E+308.
2. MIN_VALUE It returns the smallest possible value of a number in JavaScript and can have 5E-324.
3. NEGATIVE_INFINITY It returns a value that is less than MIN_VALUE.
4. POSITIVE_INFINITY It returns a value that is greater than MAX_VALUE.
5. NaN When some number calculation is not representable by a valid number, then TypeScript returns a value NaN. It is equal to a value that is not a number.
6. prototype It is a static property of the Number object. It is used to assign new properties and methods to the Number object in the current document.

例

console.log("Number Properties: "); 
console.log("A number variable can hold maximum value: " + Number.MAX_VALUE); 
console.log("A number variable can hold minimum value: " + Number.MIN_VALUE); 
console.log("Value of Negative Infinity: " + Number.NEGATIVE_INFINITY); 
console.log("Value of Positive Infinity:" + Number.POSITIVE_INFINITY);
console.log("Example of NaN: " +Math.sqrt(-5)); // NaN

输出：

Number Properties: 
A number variable can hold maximum value: 1.7976931348623157e+308
A number variable can hold minimum value: 5e-324
Value of Negative Infinity: -Infinity
Value of Positive Infinity: Infinity
Example of NaN: NaN

编号方法

下面列出了Number方法及其说明。

SN Method_Name Description
1. toExponential() It is used to return the exponential notation in string format.
2. toFixed() It is used to return the fixed-point notation in string format.
3. toLocaleString() It is used to convert the number into a local specific representation of the number.
4. toPrecision() It is used to return the string representation in exponential or fixed-point to the specified precision.
5. toString() It is used to return the string representation of the number in the specified base.
6. valueOf() It is used to return the primitive value of the number.

例

let myNumber: number = 12345;
let myNumber_1: number = 12.8789;
let myNumber_2: number = 12667.976;
let myNumber_3: number = 12.5779;
let myNumber_4: number = 1234;
let myNumber_5 = new Number(123);

console.log("Number Method: toExponential()");
console.log(myNumber.toExponential()); 
console.log(myNumber.toExponential(2));

console.log("Number Method: toString()");
console.log(myNumber.toString());
console.log(myNumber.toString(4));

console.log("Number Method: toFixed()");
console.log(myNumber_1.toFixed());
console.log(myNumber_1.toFixed(3));

console.log("Number Method: toLocaleString()");
console.log(myNumber_2.toLocaleString()); // returns in US English

console.log("Number Method: toPrecision()");
console.log(myNumber_3.toPrecision(1)); 
console.log(myNumber_3.toPrecision(3));

console.log("Number Method: tovalueOf()");
console.log(myNumber_5)
console.log(myNumber_5.valueOf())
console.log(typeof myNumber)

输出：

Number Method: toExponential()
1.2345e+4
1.23e+4
Number Method: toString()
12345
3000321
Number Method: toFixed()
13
12.879
Number Method: toLocaleString()
12,667.976
Number Method: toPrecision()
1e+1
12.6
Number Method: tovalueOf()
[Number: 123]
123
number