JavaScript-based arithmetic operators, back-and-forth increment/decrement operators, comparison operators, logical operators, program flow control

1. Arithmetic Operators

Add, subtract, multiply, divide, and balance, where % is the remainder operation

+ operator

A. If the plus sign is a string, then the plus sign is connected.

B. If both sides of the plus sign are numeric, then the plus sign is added.

C. If the plus sign is a string, the function of the plus sign is to connect.

var num1 = 123var string1 = "123" Console.log (NUM1 + string1)//This is the + operator is the link effect, the result is 123123console.log (NUM1 + num1)  //Both sides are number Value, the + operator is additive, and the result is 246

the -operator is an operation between two numeric values. The * operator is the multiplication of two values The /operator is the division of two values residual, modulus remainder:10/3 = 3.....1; 1 is the remainder .

Shorthand for the operator:

A = a + 2;   A + = 2;a = A-2;   A-=2;a = a * 2;   A*=2;a = A/2;   A/= 2;a = a% 2;  a%=2;

　　

　 2. Self increment/decrement operator + +,--

Self-increment:

    var a = 1;    var B = 2;

First add: ++a;

var C = A + + b++;//usually see first plus, first calculate Gaga,//And then calculate

After add: a++;

var c = ++a  +  ++b;  All see after Add, first to remove Gaga, remove after the calculation//To obtain the results after the self-gaga

self-reducing--a and a--are also

3. Comparison operator (<, >=, <=, = =,!=,===,!==)

Alert (> 5);//true

　　

var i = 100;var n = 100;alert (i = = n);//true;alert (i! = n);//false;        alert (i = = N)         

　　

4. Logical operators (&&, | |,!)　

&&: Logic and (and)

&& Features: A flase is false

|| : Logical OR (OR)

|| Feature: A true is true.

！ : Logical non (take reverse)

var i = 8;alert (i<5 && i<10);  False (i > | | i <);  True (! ( > 5));  False

　　

precedence of logical operators:

! > && > | |

() >*,/> +,-

　5. Program Flow Control

If ... else structure:

if (condition) {code One}else {Code II}

If...else If ... else:

if (condition) {code block 1}else if (condition/boolean) {code block 2}else {code block 3}

　　

Switch Case:

Switch (variable) {case Variable value 1: code block 1;break;case Variable Value 2: code block 2;break;case Variable Value 3: code block 3;break;.....default: Default code block; break;}

　　

Attention:

1.case can have any number of

2.case must have a break in the knot part.

The colon after the variable value of 3.case

4.default can write or not write, but if you do not write, the conditional code will be terminated directly.

JavaScript-based arithmetic operators, back-and-forth increment/decrement operators, comparison operators, logical operators, program flow control