JavaScript comparison and logical operators

Comparison operator

Operator Description Example Operation Result

##== Equal to 2 == 3 FALSE

=== Constantly equal (both values and types are compared) (2 === 2 TRUE) (2 === "2" FALSE )

!= Not equal to, can also be written as <> 2 == 3 TRUE

> Greater than 2 > 3 FALSE

< Less than 2 < 3 TRUE

>= Greater than or equal to 2 >= 3 FALSE

<= Less than or equal to 2 <= 3 TRUE

Comparison operators can also be used for string comparisons.

<!DOCTYPE html>
<html>
<head> 
<meta charset="utf-8"> 
<title>php中文网(php.cn)</title> 
    <script type="text/javascript">
        var a=5,b="5";
        document.write(a==b);
        document.write("<br />");
        document.write(a===b);
        document.write("<br />");
        document.write(a!=b);
        document.write("<br />");
        document.write(a!==b);
    </script>
</head>
<body>
</body>
</html>

##Logical operators

Operator

Explanation

Example Operation result

#&& Logical AND (and) x = 2 ; y = 6; x && y > 5 FALSE

|| Logical OR (or) x = 2; y = 6; , take the opposite side of logic x = 2; y = 6; !(x > y) TRUE

<!DOCTYPE html>
<html>
<head> 
<meta charset="utf-8"> 
<title>php中文网(php.cn)</title> 
    <script type="text/javascript">
        var a=5,b="5";
        document.write(a&&b > 10);
        document.write("<br />");
        document.write(a||b <6);
        document.write("<br />");
        document.write(!(a>b));
      </script>
</head>
<body>
</body>
</html>

Conditional Operator

JavaScript also includes conditional operators that assign values to variables based on certain conditions.

Syntax

variablename=(condition)?value1:value2

<!DOCTYPE html>
<html>
<head> 
<meta charset="utf-8"> 
<title>php中文网(php.cn)</title> 
</head>
<body>
年龄:<input id="age" value="18" />
<p>是否达到上学年龄?</p>
<button onclick="myFunction()">点击按钮</button>
<p id="demo"></p>
<script>
function myFunction()
{
var age,voteable;
age=document.getElementById("age").value;
voteable=(age<7)?"年龄太小，继续幼儿园":"年龄已达到，可以入学";
document.getElementById("demo").innerHTML=voteable;
}
</script>
</body>
</html>

Continuing Learning

new file

<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>php中文网(php.cn)</title> <script type="text/javascript"> var a=5,b="5"; document.write(a==b); document.write("<br />"); document.write(a===b); document.write("<br />"); document.write(a!=b); document.write("<br />"); document.write(a!==b); </script> </head> <body> </body> </html>

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Automatic operation

JavaScript comparison and logical operators

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