Summary of JavaScript operator usage-JS Tutorial-php.cn

Summary of JavaScript operator usage

巴扎黑

Release： 2017-07-29 17:14:17

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This article mainly gives you a detailed summary of the operators in JavaScript, including common arithmetic operators, comparison operators and logical operators. It is very clear, friends who need it can refer to it.

In JavaScript, common operators include arithmetic operators, comparison operators and logical operators.

Table 1 JavaScript common operators

##--decrement. Decrement the operand by 1. n=--x;n=5 x=5##Comparison operator==##!=Not equal. If the two data are not equal, return true, otherwise return false. boolean2=(x!=5);boolean2=false;> is greater than. If the data on the left is greater than the data on the right, return true, otherwise return false. boolean4=(x>y);boolean4=true< is less than. If the data on the left is less than the data on the right, a Boolean value true is returned, otherwise false is returned. boolean5=(xboolean5=false>=Greater than or equal to. If the data on the left is greater than or equal to the data on the right, return true, otherwise return false. boolean6=(x>=y);boolean6=true<=Less than or equal to. If the data on the left is less than or equal to the data on the right, return true, otherwise return false. boolean7=(x<=y);boolean7=falseLogical operatorDescriptionExampleResult&&Logical AND. Returns true if the operands on both sides of the symbol are true, otherwise returns false. boolean_a=true&&false;boolean_a=false||Logical OR. If the operands on both sides of the symbol are false, return false, otherwise return true. boolean_b=true||false;boolean_b=true!Logical negation. Returns false if the operand to the right of the symbol is true, otherwise returns true. boolean_c=!true;boolean_c=false" + " sign can also be used to concatenate strings

Arithmetic operators	Explanation	Examples	Result
=	Assignment operator. Assign the value of the variable on the right side of the operator to the variable on the left.	x = 5;	-
+	plus sign. Add two numbers.	y=1+2;	y=3
-	Minus sign. Subtract two numbers.	z = x-y;	z=2
*	Multiply sign. Multiply two data together.	a=x*y;	a=15
/	Division sign. Divide two data.	b=x/z;	b=2.5
%	Remainder operation. Find the remainder after dividing two numbers.	c=x%z;	c=1
++	Self-added. Add 1 to the operand.	m=++x;	m=6 x=6

Description	Example	Result
Equal. If the two data are equal, return true, otherwise return false.	boolean1=(x==5);	boolean1=true

The "+" sign can not only add two data, but can also be used to connect strings.

For example:

The code is as follows:

 var name=" Tom ";
 var age=22;
 var person="My name is "+name+" ! I&#39;m  "+age+" ! ";
 alert(person);

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Save and run the code to display My name is Tom! I'm 22!

In the above example , including strings and numerical values. When strings and numerical values are mixed, JavaScript will automatically determine whether the "+" sign is used for addition or concatenation of strings. If concatenating strings, the numeric value will also be converted to a string.

Discussion on self-increasing (++) and self-decreasing (--)

It is worth noting that self-increasing (++) and self-decreasing (- -) The operator has different meanings when placed before and after the operand. If it is placed in front of the operand (front self-increment/front self-decrement), the operand will be added by 1 (subtracted by 1) first, and then the operation will be performed; if it is placed after the operand (last self-increment/back self-decrement), the operation will be performed first. Then add 1 to the operand (decrease 1).

For example:

The code is as follows:

 <script type="text/javascript">
 var x=5;
 var y=++x;  // 前自加，赋值后 x 的值为 6
 var z=x++;  // 后自加，赋值后 x 的值为 7
 var m=--x  // 前自减，赋值后 x 的值为 6
 var n=x--  // 后自减，赋值后 x 的值为 5
 </script>
 <p onclick="alert(y);">显示 y 的值</p>
 <p onclick="alert(z);">显示 z 的值</p>
 <p onclick="alert(m);">显示m 的值</p>
 <p onclick="alert(n);">显示 n 的值</p>

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Save and run the code, click on the four pieces of text in sequence, and all of them will display 6.

Analysis:

For y, the value of x (x=5) plus 1 becomes 6, and then the value of x is passed to y.

For z, first pass the value of x (x=6) to z, then add 1 to x, and the value becomes 7.

For m, the value of x (x=7) minus 1 is 6, and then the value of x is passed to m.

For n, first pass the value of x (x=6) to n, then subtract 1 from x, and the value becomes 5.

Abbreviations of arithmetic operators

In order to facilitate operation and reduce code writing, JavaScript also supports abbreviations of common mathematical operators.

Table 2 Abbreviations of common arithmetic operators

OperatorExample is equivalent to +=x+=yx=x+y-=x-=yx=x-y*=x*=yx=x*y/=x/=yx=x/y%=x%=yx=x%y

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