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 TRUEComparison 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
ExplanationExample 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>
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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