Introduction to the use of Javascript bitwise AND assignment operator (&=)_Basic knowledge

Javascript bitwise AND assignment operator (&=) sets the result of the bitwise AND operation between variable value and expression value. Variables and expressions are regarded as 32-bit binary values, and general expressions contain decimal integers. In this case, they need to be converted into the corresponding binary first, and then 0 is added forward to make up the 32 bits.

Copy code The code is as follows:

result &= [integer 2]
equivalent In
result = result & [integer 2]

& performs a bitwise AND operation on each bit of two 32-bit expressions. If both bits are 1, the result is 1. Otherwise, the result is 0.

位1	位2	位与
0	0	0
1	1	1
0	1	0
1	0	0

The following example demonstrates how to use the & bitwise AND operator and the &= bitwise AND assignment operator:

Copy code The code is as follows:

// 9 The binary value is 1001, and the 32-digit complement is 0000000000000000000000000000100 1
var expr1 = 9;

// 5 is 00000000000000000000000000000101
var expr2 = 5;

/*
00000000000000000000000000001001
&
000000000000000000000000000000101
=
00000000000000000 00000000000001
=
1
*/

var result = expr1 & expr2 ;

alert(result);
//pop up【1】

expr1 &= expr2;
alert(expr1);
// Pop up【1】

JavaScript assignment operators and expressions


JavaScript assignment operators are responsible for assigning values ​​to variables. JavaScript assignment operators include =, =, -=, *=, / =, %=
An expression that is connected with the assignment operator and the operand (operand) and conforms to the regular JavaScript syntax is called a JavaScript assignment expression.

JavaScript assignment operator and assignment expression syntax

var i =a;

= -- assignment operator
The meaning of the above expression is: change i The value obtained by adding a is assigned to variable i.

JavaScript assignment operators and assignment expressions

Operator	=	=	-=	*=	/=	%=

运算符	=	=	-=	*=	/=	%=
名称	赋值运算符	加法赋值运算符	减法赋值运算符	乘法赋值运算符	除法赋值运算符	模赋值运算符(求余赋值运算符)
表达式	i=6	i =5	i-=5	i*=5	i/=5	i%=5
示例	var i=6;	i =5;	i-=5;	i*=5;	i/=5;	i%=5;
i的结果	6	11	1	30	1.2	1
等价于		i=i 5;	i=i-5;	i=i*5;	i=i/5;	i=i%5;

Name Assignment operator
Addition assignment operator
Subtraction assignment operator
Multiplication assignment operator
Division assignment operator
Modular assignment operator (remainder assignment operator)

Expression i=6 i =5 i-=5 i*=5 i/=5 i%=5

Example var i=6;
i =5;
i-=5;
i*=5;
i/=5;
i%=5;

i's results 6
11
1
30
1.2
1

Equivalent to
i=i 5; i=i-5;
i=i*5;
i=i/5;
i=i%5;

Example explanationThere is an essential difference between the pre-increment operator and the post-increment operator. The same point is that 1 is added to itself. The difference is that the pre-increment operator first adds 1 and then uses the value of the operand. The post-increment operator first uses the value of the operand and then adds 1. For example:

Copy code

The code is as follows: var a; var i=6; //(Add before adding) After adding 1 to i, i equals 7, and assigns the value of i to a, so a equals 7 a= i; document.write (i); document.write(a); i=6; //(add after) assign the i value to a, so a is equal to 6, and finally i adds 1, i equals 7 a=i; document.write(i); document.write(a); Result: Copy code The code is as follows: 7 7 7 6