Detailed JS operator single vertical bar "|" and "| |" Introduction to the use and role of the basic knowledge

In the JS development application we usually encounter the "|" and "| |" , then in the operation "|" and "| |" What does it mean?

In the JS integer operation, the equivalent of removing the decimal point, parseint. When a positive number is equivalent to Math.floor (), a negative number is equivalent to the Math.ceil () Note:

1. Math.ceil () is used for rounding up.
2. Math.floor () is used as a downward rounding.
3. Math.Round () The rounded rounding we used in maths.

Console.log (0.6|0)//0
console.log (1.1|0)//1 console.log
(3.65555|0)//3 console.log
(5.99999|0)//5
Console.log ( -7.777|0)//-7

Rule of operation of single vertical bar

Look at the above example, the general know that a single vertical bar can be used to take the whole operation, that is, only the positive part, the decimal part by taking off, but "|", and how to operate it, why can "|" to achieve the purpose of rounding? The single vertical bar is not 0 What is the number?

With these questions, let's look at the following examples:

Console.log (3|4); 7
Console.log (4|4);//4 Console.log (8|3);//11 Console.log (5.3|4.1);//5 console.log
(9|3455); /3455

This refers to the single vertical bar "|" But there's no JavaScript.

All right, I'm here to announce the answer. In fact, single vertical bar "|" Is the result of the addition of the conversion to the 2 binary. For example, let's take a simple example:

3|4

After converting to binary 011|100 add to 111=7

4|4

After converting to binary 100 |100 add to get 100=4

8|3

After converting to binary 1000 |011 add to get 1011=11

And so on, I'm not going to enumerate here, single vertical bar "|" The operation is to convert to 2 after the addition of the result!

JS Double vertical bar operator

1, JS double vertical line operator: is or comparison. such as null| | ' 1 ', return ' 1 '; 2 ' | | ' 1 ', return ' 2 '. The first is true, and the back is not calculated. So ' 2 '.

2, JS using the double vertical bar operator "| |", return the first valid value

var objone = undefined | | 1 | | null | | New Date (); 
var objtwo = new Date (); 
var objthree = Objone | | Objtwo; 
Alert (objthree.tostring ()); Out put "1"

Summarize

Performance comparisons

Logical Operators && | | , if the && 's first shipping count is false, the second operand is no longer considered and returns false directly; The first op count is true, and the second operand is no longer considered, and returns true directly. The & and | operators are not, and they always have to compare two operands to get results, so performance && and | | would be better than & and |

Functional usage

&& and | | Only logical operations can be performed, and & and | In addition to being able to perform "logical operations", bitwise operations

Bit operations

& and | This is a bit operator, the reason for "logical operation" is because JS is a language of no type, the data types can be freely converted by the characteristics of the decision, when using & and | "Logical operation", actually true is converted to 1,false is converted to 0, The bitwise-BY Operation:

Document.Write (True & false); JS, the result is 0

In the preceding sentence, an instance is equivalent to a logical operation being converted to the following bitwise operation and executing:

document.write (1 & 0); JS, the result is 0

It is also because & and | are bitwise operators that appear in the 1th, they always have to compare two operands to produce results, which will result in performance than && and | | A little lower.

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