Explanation on the use of js operators single vertical bar '|' and '||'

In js development applications, we usually encounter "|" and "||", so what do "|" and "||" mean in operations? This article mainly introduces the detailed explanation of the usage of js operators single vertical bar "|" and "||". You can learn more if you need it.

In js development applications, we usually encounter "|" and "||", so what do "|" and "||" mean in operations?

When performing js integer operations, it is equivalent to removing the decimal point, parseInt. When it is a positive number, it is equivalent to Math.floor(), when it is a negative number, it is equivalent to Math.ceil() Note:

1. Math.ceil() is used to round up.
2. Math.floor() is used to round down.
3. Math.round() Rounding is commonly used in our mathematics.

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

Operation rules of single vertical bars

After reading the above example, we generally know that single vertical bars can be used for rounding operations , that is, only the positive part is retained, and the decimal part is removed. But how is "|0" calculated? Why can "|0" achieve the purpose of rounding? If the horizontal and vertical bar is not 0, what would it be?

With these questions, let’s look at the following example:

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

The horizontal and vertical bar "|" is mentioned here but there is no javascript.

Okay, let me announce the answer here. In fact, the single vertical bar "|" is the result of the addition after converting to binary. For example, let’s take a simple example:

3|4

After converting to binary, 011|100 is added to get 111=7

4|4

After converting to binary, 100 | 100 is added to get 100=4

8|3

After being converted to binary, 1000 | 011 is added to get 1011=11

By analogy, I will not list them one by one here. The single vertical bar "|" operation is the result of the addition after converting to binary!

JS double vertical bar operator

1. JS double vertical bar operator: yes or comparison. Such as null||'1', return '1'; '2'||'1', returns '2'. That is, in the OR operator, the first one is true, and the following ones do not need to be calculated. So we get '2'.

2. Use the double vertical bar operator "||" in js to 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"

Summary

Performance comparison

In the logical operator && ||, if the first operand of && is false, the second operand will not be considered operand, return false directly; if the first operand of || is true, the second operand will not be considered, and true will be returned directly. This is not the case with the & and | operators. They always need to compare two operands to get the result, so the performance of && and || will be better than & and |.

Function Usage

&& and || can only perform logical operations, while & and | can not only perform "logical operations", but also perform bit operations

Bit operations

&| are originally bit operators. The reason why "logical operations" can be performed is because JS is a typeless language and each data type can be freely Determined by this feature of conversion, when using & and | to perform "logical operations", true is actually converted to 1, false is converted to 0, and then bit-by-bit operations are performed:

document.write(true & false); //JS，结果为0

The above sentence is equivalent to logical operations being converted into the following bit operations and executed:

##

document.write(1 & 0); //JS，结果为0

It is precisely because & and | are sequential Bitwise operators appear as mentioned in the first point. They always need to compare two operands to get the result, which results in lower performance than && and ||.

The above is what I compiled for everyone. I hope it will be helpful to everyone in the future.

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