** Concept **

Math yes javaScript Built in objects for , It includes some mathematical constant attributes and mathematical function methods .

Math It's not a function object , user Number Type , I won't support it BigInt.

Math All properties and methods of are static .

For example, when we use pi , It's written in Math.PI

When using the sine and cosine function, the expression is Math.sin(x),x Is the parameter to pass in .

Math The constant used is JavaScript Defined by the full precision floating-point number in .

**math Native properties **

// Euler constant , It is also the base of natural logarithm , About equal to 2.718.

console.log("Math.E", Math.E); // Math.E 2.718281828459045

// 2 The natural logarithm of , About equal to 0.693.

console.log("Math.LN2", Math.LN2); // Math.LN2 0.6931471805599453

// 10 The natural logarithm of , About equal to 2.303.

console.log("Math.LN10", Math.LN10); // Math.LN10 2.302585092994046

// With 2 At the bottom of the E The logarithmic , About equal to 1.443.

console.log("Math.LOG2E", Math.LOG2E); // Math.LOG2E 1.4426950408889634

// With 10 At the bottom of the E The logarithmic , About equal to 0.434.

console.log("Math.LOG10E", Math.LOG10E); // Math.LOG10E 0.4342944819032518

// PI , The ratio of the circumference of a circle to its diameter , About equal to 3.14159.

console.log("Math.PI", Math.PI); // Math.PI 3.141592653589793

// Calculate the circumference of the circle

function calculateCircumference(radius) {

return 2 * Math.PI * radius;

}

console.log("calculateCircumference(1)", calculateCircumference(1)); // calculateCircumference(1) 6.283185307179586

// A half ½ The square root of , It's also 2 The reciprocal of the square root of 1 2 , About equal to 0.707.

console.log("Math.SQRT1_2", Math.SQRT1_2); // Math.SQRT1_2 0.7071067811865476

// 2 The square root of , About equal to 1.414.

console.log("Math.SQRT2", Math.SQRT2); // Math.SQRT2 1.4142135623730951

**math Common methods **

`Math.abs() // Specify the number “x“ The absolute value of `

Math.abs("-1"); // 1

Math.abs(-2); // 2

Math.abs(null); // 0

Math.abs("string"); // NaN

Math.abs(); // NaN

**math Digital processing methods in daily development **

`// Math.round() Function returns the nearest integer to which a number is rounded .`

console.log(Math.round(20.49)); //20

console.log(Math.round(20.5)); //21

console.log(Math.round(-20.5)); //-20

console.log(Math.round(-20.51)); //-21
// Math.ceil() Returns the smallest integer greater than or equal to a given number , Rounding up .

console.log(Math.ceil(0.95));

// 1

console.log(Math.ceil(4));

// 4

console.log(Math.ceil(7.004));

// 8

console.log(Math.ceil(-7.004));

// -7
// Math.floor() Returns the maximum integer less than or equal to a given number , Math.floor() To round down .

Math.floor(45.95);

// 45

Math.floor(45.05);

// 45

Math.floor(4);

// 4

Math.floor(-45.05);

// -46

Math.floor(-45.95);

// -46
// Math.max() Returns the maximum value of a set of numbers

console.log(Math.max(1, 3, 2));

// 3

console.log(Math.max(-1, -3, -2));

// -1

const array1 = [1, -3, 2];

console.log(Math.max(...array1));

// 3
// Math.min() Returns the minimum value of zero or more values .

console.log(Math.min()); // Infinity

console.log(Math.min(1, 2, 3, -4)); // -4
// Use Math.min() Crop value （Clipping a value）

function f(x) {

if (x > 5) {

return (x = 5);

}

return (x = 6);

}

var finalMin = Math.min(f(2), 2, 3, 4, 5, 30);

console.log("finalMin", finalMin); // 2
// Math.sqrt() Returns the square root of a number

function calcHypotenuse(a, b) {

return Math.sqrt(a * a + b * b);

}

console.log(calcHypotenuse(3, 4));

// 5

console.log(calcHypotenuse(5, 12));

// 13

console.log(calcHypotenuse(0, 0));

// 0

** Use Math.random() Generate random number **

`/**`

*

* Math.random() Function returns a floating point number

* Pseudo random numbers in the range from 0 To less than 1, in other words , from 0（ Include 0） Upward , But not including 1（ exclude 1）,

* Then you can zoom to the desired range . Implement the initial seed selection to the random number generation algorithm ; It cannot be selected or reset by the user .

*

* */
console.log(Math.random());
function getRandomNumber(min, max) {

min = Math.ceil(min);

max = Math.floor(max);

return Math.floor(Math.random() * (max - min + 1)) + min; // Including the maximum value , Including the minimum value

}
console.log(getRandomNumber(2, 100));

** Summary **

- The above examples include math Common methods and properties api
- math In use , Can combine random as well as max and min Such method , Generate the required random number
- adopt round、floor、ceil, We can take further values for numbers , Get a number format that meets the requirements

Math For more information, please refer to the documentation

**Mathjs plug-in unit **

** Document address **

https://mathjs.org/examples/index.html

mathjs The method provided by the plug-in is relatively comprehensive , It covers everything from algebraic calculations to functional calculations , Money calculation and other methods , Matrix serialization, etc , More ways to view official documents .

Basic usage ：

```
npm install mathjs
import { sqrt } from 'mathjs'
console.log(sqrt(-4).toString()) // 2i
```

#### Source code address

**Code cloud**https://gitee.com/lewyon/vue-note**githup**https://github.com/akari16/vue-note

Article personal blog address ：javaScript in Math Introduction to basic methods of built-in objects

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