JavaScript comparison
Comparison and logical operators are used to test true or false.
Comparison operators
Comparison operators are used in logical statements to determine whether variables or values are equal.
x=5, the following table explains the comparison operators:
==:
Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
</head>
<body>
<p>x=5, 返回 x==8 的比较值结果。</p>
<button onclick="myFunction()">尝试一下</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x=5;
document.getElementById("demo").innerHTML=x==8;
}
</script>
</body>
</html>Run Instance»
Click the "Run Instance" button to view the online instance
Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
</head>
<body>
<p>x=5, 返回 x==5 的比较值结果。</p>
<button onclick="myFunction()">尝试一下</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x=5;
document.getElementById("demo").innerHTML=x==5;
}
</script>
</body>
</html>Run Instance»
Click "Run Instance" "Button to view online examples
===:
##Examples
Run Instance»Click the "Run Instance" button to view the online instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
</head>
<body>
<p>x=5, 返回 x==="5" 的比较值结果。</p>
<button onclick="myFunction()">尝试一下</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x=5;
document.getElementById("demo").innerHTML=x==="5";
}
</script>
</body>
</html>Run Instance»Click the "Run Instance" button to view the online instance
##Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
</head>
<body>
<p>x=5, 返回 x===5 的比较值结果。</p>
<button onclick="myFunction()">尝试一下</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x=5;
document.getElementById("demo").innerHTML=x===5;
}
</script>
</body>
</html>
Run Instance»Click the "Run Instance" button to view the online instance
##Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
</head>
<body>
<p>x=5, 返回 x!=8 的比较值结果。</p>
<button onclick="myFunction()">尝试一下</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x=5;
document.getElementById("demo").innerHTML=x!=8;
}
</script>
</body>
</html>Running Instance»
Click the "Run Instance" button to view the online instance!==:
Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
</head>
<body>
<p>x=5, 返回 x!=="5" 的比较值结果。</p>
<button onclick="myFunction()">尝试一下</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x=5;
document.getElementById("demo").innerHTML=x!=="5";
}
</script>
</body>
</html>Run Instance»
Click the "Run Instance" button to view the online instance
Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
</head>
<body>
<p>x=5, 返回 x!==5 的比较值结果。</p>
<button onclick="myFunction()">尝试一下</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x=5;
document.getElementById("demo").innerHTML=x!==5;
}
</script>
</body>
</html>Run Instance»
Click the "Run Instance" button to view the online instance >:
##Example
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
</head>
<body>
<p>x=5, 返回 x>8 的比较值结果。</p>
<button onclick="myFunction()">尝试一下</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x=5;
document.getElementById("demo").innerHTML=x>8;
}
</script>
</body>
</html>##Example
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
</head>
<body>
<p>x=5, 返回 x<8 的比较值结果。</p>
<button onclick="myFunction()">尝试一下</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x=5;
document.getElementById("demo").innerHTML=x<8;
}
</script>
</body>
</html>Run Instance»
Click the "Run Instance" button to view the online instance
>=:
Instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
</head>
<body>
<p>x=5, 返回 x>=8 的比较值结果。</p>
<button onclick="myFunction()">尝试一下</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x=5;
document.getElementById("demo").innerHTML=x>=8;
}
</script>
</body>
</html>Run Instance»
Click the "Run Instance" button to view the online instance
<=:
##Example
Run Instance»Click the "Run Instance" button to view the online instance
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>php中文网(php.cn)</title>
</head>
<body>
<p>x=5, 返回 x<=8 的比较值结果。</p>
<button onclick="myFunction()">尝试一下</button>
<p id="demo"></p>
<script>
function myFunction()
{
var x=5;
document.getElementById("demo").innerHTML=x<=8;
}
</script>
</body>
</html>Run Instance»Click the "Run Instance" button to view the online instance
How to use
You can use comparison operators in conditional statements to compare values and then take action based on the results:
if (age<18) x="Too young ";
#You will learn more about conditional statements in the next section of this tutorial.
Logical Operators
Logical operators are used to determine the logic between variables or values.
Given x=6 and y=3, the following table explains the logical operators:
| Description | Example | |
|---|---|---|
| and | (x < 10 && y > 1 ) is true | |
| or | (x==5 || y==5) is false | |
| not | !(x==y) is true |
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>
<p>点击按钮检测年龄。</p>
年龄:<input id="age" value="18" />
<p>是否达到投票年龄?</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<18)?"年龄太小":"年龄已达到";
document.getElementById("demo").innerHTML=voteable;
}
</script>
</body>
</html>
Run Instance»Click the "Run Instance" button to view the online instance
