7. JavaScript Operators

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JavaScript Arithmetic Operators

Arithmetic operators are used to perform common mathematical operations such as addition, subtraction, multiplication, division, etc.

operator	name	example
+	addition	x + y means to calculate the sum of x plus y
-	subtraction	x - y means calculate the difference between x minus y
*	multiplication	x * y means to calculate the product of x times y
/	division	x / y means to calculate the quotient of x divided by y
%	modulo (remainder)	x % y means to calculate the remainder of dividing x by y
++	self-increment	++x adds 1 to x and returns the value of x
		x++ returns the value of x, then adds 1 to x
- -	Decrement	- -x subtract 1 from x and return the value of x
		x-- returns the value of x, then decrements x by 1

var x = 10,
var y = 5;
console.log("x + y =", x + y);
console.log("x - y =", x - y); 
console.log("x * y =", x * y);
console.log("x / y =", x / y);
console.log("x % y =", x % y);

let x = 5;
x++;

let y = 5;
y--;

let x = 5;
let y = x++;
let z = ++x; 

JavaScript assignment operator

Assignment operators are used to assign values ​​to JavaScript variables.

operator	describe	example	Equivalent to
=	The simplest assignment operator, which assigns the value on the right side of the operator to the variable on the left side of the operator	x=y	Assign variable x to y
+=	Do the addition first, then assign the result to the variable on the left side of the operator	x+=y	x=x+y
-=	Perform the subtraction first, then assign the result to the variable on the left side of the operator	x-=y	x=x-y
*=	Do the multiplication first, then assign the result to the variable on the left side of the operator	x*=y	x=x*y
/=	Perform division first, then assign the result to the variable on the left side of the operator	x/=y	x=x/y
%=	First perform the modulo operation, and then assign the result to the variable on the left side of the operator	x%=y	x=x%y

var x = 10;
x += 20;
console.log(x); 
var x = 12,
    y = 7;
x -= y;
console.log(x); 
x = 5;
x *= 25;
console.log(x);
x = 50;
x /= 10;
console.log(x); 
x = 100;
x %= 15;
console.log(x);

JavaScript string operators

• Operators are used to add (concatenate) text values ​​or string variables.
  To concatenate two or more string variables, use the + operator.

var x = "Hello ";
var y = "World!";
var z = x + y;
console.log(z);
x += y;
console.log(x); 

JavaScript comparison operators

The comparison operator is used to compare the expressions on the left and right sides of the operator. The operation result of the comparison operator is a Boolean value, and there are only two results, either true or false.

operator	name	example
==	equal	x == y means true if x is equal to y
===	congruent	x === y means true if x is equal to y, and x and y are also of the same type
!=	not equal	x != y means true if x is not equal to y
!==	Insufficiency, etc.	x !== y means true if x is not equal to y, or x and y are of different types
<	less than	x < y means true if x is less than y
>	more than the	x > y means true if x is greater than y
>=	greater than or equal to	x >= y means true if x is greater than or equal to y
<=	less than or equal to	x <= y means true if x is less than or equal to y

var x = 25;
var y = 35;
var z = "25";

console.log(x == z); 
console.log(x === z); 
console.log(x != y); 
console.log(x !== z);
console.log(x < y);
console.log(x > y);
console.log(x <= y);
console.log(x >= y);

JavaScript Logical Operators

Logical operators are usually used to combine multiple expressions. The result of a logical operator is a Boolean value, which can only have two results, either true or false. The following table lists the logical operators supported in JavaScript:

operator	name	example
&&	logic and	x && y means true if both x and y are true
||	logical or	x || y means true if either x or y is true
!	logical NOT	!x means true if x is not true

var a = true;
var b = true;

if(a && b){
    
    console.log('逻辑与')}
if(a || b){
    
    console.log('逻辑或')}
if(!a){
    
    console.log('逻辑非')}

JavaScript ternary operator

The ternary operator (also known as the conditional operator) consists of a question mark and a colon. The syntax is as follows:
conditional expression? expression1: expression2;
if the result of the "conditional expression" is true (true ), execute the code in "Expression 1", otherwise execute the code in "Expression 2".

var x = 1,
  y = 2;
x > y ? console.log("x 大于 y") : console.log("x 小于 y");