Basic JavaScript knowledge summary (3) comparison operators and logical operators

This time I will bring you a basic knowledge summary of JavaScript. There are a total of eleven knowledge points. Basic JavaScript knowledge summary (3)Comparison operators, Logical operator, the following is a practical case, let’s take a look.

Write at the front

js (2) mentioned simple addition, subtraction, multiplication and division. Now let’s talk about the other two operators

Comparison operators

“>”、“<”、“==”、“>=”、“<=”、“!=”

The result of the comparison is a boolean value

Logical operator

“&&”、“||”、“!”

The result of the operation is the real value

The value that is considered false

undefined、null、NaN、""、0、false

Calculation Operator

var a = 10,
    b = 20,
    c;
    c = a < b;//true
    c = a > b;//false
    c = "a" > "b"//false,比较的ascll码值
    c = a == b// false
    c = a != b//false
    c = NaN == NaN//false,NaN不等于任何数;

Logical operator

//Logical AND &&var a = 1 && 2//Print out a-->2//Logical OR||var a = 1 || 3;//Print out a-->1//Logical not! Convert to Boolean value and invert var a = !123;//false;

Logical AND&& Let’s look at the first one first The result of converting an expression to a Boolean value. If it is true, then it will look at the result of converting the second expression to a Boolean value. Then if there are only two expressions, it will only look at the second one. Expression, you can return the value of the expression, a short-circuit statement;

I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

Related reading:

Summary of basic JavaScript knowledge (2) Introduction, variables, value types, operators

Summary of basic JavaScript knowledge (1)

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