What are the js operators? Detailed introduction to js operators

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javascript basic operators are divided into: arithmetic operators, assignment operators, relational operators, logical operators; the following is a detailed explanation of how to master several operators;

(1) Arithmetic operators

1. Arithmetic operators can be divided into unary operators, binary operators, and ternary operators according to the different operands on both sides of the operator;

2. According to different functions, it is divided into: (plus sign), — (minus sign), (multiplication sign), / (division sign) and % (remainder operation);

1-1 .Unary operator;

(auto-increment), - - (auto-decrement);

When the operator is followed by: when assignment does not occur, the increment and self-decrement operation is performed; assignment occurs When , assign the value first and then perform the operation.

When the operator is prepended: When no assignment occurs, the increment and self-decrement operation is performed; when an assignment occurs, the operation must be performed first and then the value is assigned.

Examples of operator postpositions;

var a=3;
a++;
consonle.log(a)//值为4
 var a=3;
    var b=4;
     a--;
     b--;     
    var c=a+b;//2+3
    console.log(c);//5
var a=3;
var b=4;
a++;
b++;
var c=(a+b);//4+5
consonloe.log(c);//c的值为9
   var a=3;
    var b=4;
    var c=(a++)+a+(b++)+b;//3+4+4+5
    console.log(c);//16
 var a=3;
    var b=4; 
    var c=(a--)+a+(a++)+(b++)+b+(b--);//3+2+2+4+5+5
    console.log(c);//21

Examples of operator prepositions;

 var b=4;
 --a;//2
 ++b;//5
 console.log(a,b);//  2  5
 var a=3;
 var b=4;
 var c=--a+b;//2+4  运算符前置 先运算 再赋值。
 console.log(c);//6
 var a=3;
 var b=4;
 var c=--a+--b;//2+3 
 console.log(c);//5

Comprehensive use of pre and postpositions;

    var a=3;
     var b=4;
     var c=(--a)+(--b)+(b++);//2+3+3 
     console.log(c);//8

Let’s explain it here: Let’s first Operate it separately;

(--a)=2; Operator is prefixed, operate first and then assign value;

(--b)=3: Same as (--a);

(b)=3; Many students will calculate it as equal to 4 or 5. We need to understand (--b) in this way and convert the value of b to 3, so (b) in brackets b is actually equal to 3 (b) is indeed equal to 4 after operation, but it is clear that it is the operator postposition, so when it is added to other values, its value is 3.

Let’s look at the next example;

     var a=5;
     var b=6;
     var c=(a++)+(b--)+(--a)-(--b);//5+6+5-4
     console.log(c);//12

(a) 5

(b--) 6 These two are operator postfixes, so they still have their own values;

(--a) 5 Because the value of (a) has been calculated before, it is 6. This operator is in front, so the operation is done first and then the value is assigned;

(--b) 4 is passed down by (b--) The value is 5. The operator operates first and then assigns the value, so the final value is 4;

(2) Assignment operator "=" is a well-understood operator;

var a=251; assign a value to the statement;

relational operator;

(greater than), == (equal to), < (less than), >= (greater than or equal to), <= (less than or equal to),! = (not equal), === (true equal, congruent), =....

The operation result of the relational operator is Boolean type: true (true), false (false);

, < ;, ==, >=, =< are all used to compare numerical types. The comparison methods and algorithms are the same as numeric strings; each relational operator will return a Boolean value;

  var a="3";
   var b="5";
   var c=a<b;
   console.log(c);//true
   var a=5;
   var b=8;
   var c=a<b;
   console.log(c);//true

letter type characters Strings can also be compared using greater than less than; the code point value of

  var a="alpha";
     console.log(a,typeof a);
     var b="blue";
     console.log(b,typeof b);
        var c=a<b;
     console.log(c,typeof c);//true

"a" is 97
"b"'s code point value is 98

"b"'s code point value is 98
Arrange in ascending order according to ASCII character order;

== can be used to compare numerical and numeric strings; For example;

   var b='5';
   var c=a==b;
   console.log(c);//true

=== is more advanced than ==. It is true and the two types cannot be compared. For example;

 var a=5;
   var b='5';
   var c=a===b;
   console.log(c);//false

(3) Logical operator; the output result is Boolean (boolean) type;

Logical operators are divided into three categories; logical OR | |; logical AND &&; logical NOT! ;

1. Logical OR ||: When one of the expressions on both sides evaluates to true (true), the result is true. If both sides are false, it must still be false.

Example;

      var a=3,b=4;
      var c=a>b||a<b;
      console.log(c);//true 有一侧结果为真 真个运算结果为真。
      var a=5,b=8;
      var c=a>b||a<4;
      console.log(c);//false  两边运算结果均为假 则输出结果为假 
 var a=5,b=8;
      var c=a<b||a>4;
      console.log(c);//true 两边运算结果均为真 则输出结果为真

2. Logical AND &&: The result of the operation is true only when the results on both sides of the operator are true,

Example;

      var a=5,b=8;
      var c=a<b&&a>4;
      console.log(c);//true  两边运算结果均为真 输出结果才为真
      var a=5,b=8;
      var c=a>b&&a>4;
      console.log(c);//false  两边运算结果有一侧为假 则输出结果为假
      var a=5,b=8;
      var c=a<b&&a>4;
      console.log(c);//false  两边运算结果有一侧为假 则输出结果为假

3. Logical negation! ;Get the opposite output result;

Example; This is the same as the example above. Add another! Becomes logical negation and takes the opposite value

      var a=5,b=8;
      var c=!a<b&&a>4;
      console.log(c);//true

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