JavaScript
Operators
Just about
every statement we’ll write is going to be involved an operation. To perform
lots of this operations we need operators. That means the symbols we use to
manipulate a values.
The most
obvious are probably the arithmetic operators.
|
+
|
Addition
|
|
-
|
Subtraction
|
|
*
|
Multiplication
|
|
/
|
Division
|
The equal sign is the most
used operator, called assignment operator.
Example:
<html>
<head>
<title>Untitled
Document</title>
</head>
<body>
<div
id="demo">
<h1>This
is a heading.</h1>
<p>This
is a paragraph.</p>
</div>
<script>
var a = 10;
var b = 5;
console.log(a+b);
console.log(a*b);
console.log(a-b);
console.log(a/b);
</script>
</body>
</html>
You might see
something like this:
Example:
<html>
<head>
<title>Untitled
Document</title>
</head>
<body>
<div id="demo">
<h1>This
is a heading.</h1>
<p>This
is a paragraph.</p>
</div>
<script>
var a = 10;
console.log(a
= a + 1);
</script>
</body>
</html>
In this
example to variable score is added 1. But there’s shorthand for this by adding + sign before
the equal sign. Both examples are similar.
Example:
<html>
<head>
<title>Untitled
Document</title>
</head>
<body>
<div
id="demo">
<h1>This
is a heading.</h1>
<p>This
is a paragraph.</p>
</div>
<script>
var a = 10;
console.log(a
+= 1);
</script>
</body>
</html>
Another ways:
<html>
<head>
<title>Untitled Document</title>
</head>
<body>
<div id="demo">
<h1>This is a heading.</h1>
<p>This is a paragraph.</p>
</div>
<script>
var a = 10;
console.log(a += 2);
console.log(a -= 2);
console.log(a *= 2);
console.log(a /= 2);
</script>
</body>
</html>
Multiplication and division is more important in JavaScript
so when you have code like that:
Example:
<html>
<head>
<title>Untitled Document</title>
</head>
<body>
<div id="demo">
<h1>This is a heading.</h1>
<p>This is a paragraph.</p>
</div>
<script>
var a = 10 + 5*5;
console.log(a);
</script>
</body>
</html>
Comparison operator
The equal sign is the comparison operator in JavaScript.
The single equal sign is a command.
<html>
<head>
<title>Untitled Document</title>
</head>
<body>
<div id="demo">
<h1>This is a heading.</h1>
<p>This is a paragraph.</p>
</div>
<script>
var a = 10;
var b = 20;
if (a = b) {
console.log("This
will alwasy return true.");
}
</script>
</body>
</html>
The above example will always return true because we set
an equal to the value of b, than this return true and the code in the block
will be always executed.
So remember:
One equal sign is assignment.
Two equal sign are the equality operator, you are asking.
Three equal signs is strict equality operator.
Comparisons:
If ( a == b) { … Checking equality
If ( a != b) { …
Not equal to
If ( a === b) { … Strict equality
If ( a !== b) { … Not strictly equal to
If ( a > b) { … Greater than
If ( a < b) { … Less than
If ( a >= b) { …
Greater than or equal to
If ( a <= b) { …
Less than or equal to
Sometimes we want to know if a is strictly equal to be
and and c is strictly equal to d we do that:
Example:
<html>
<head>
<title>Untitled Document</title>
</head>
<body>
<div id="demo">
<h1>This is a heading.</h1>
<p>This is a paragraph.</p>
</div>
<script>
var a = 10;
var b = 10;
var c = 30;
var d = 30;
if (a === b && c === d) {
console.log("a
is equal to be and c is equal to d");
}
</script>
</body>
</html>
OR
<html>
<head>
<title>Untitled Document</title>
</head>
<body>
<div id="demo">
<h1>This is a heading.</h1>
<p>This is a paragraph.</p>
</div>
<script>
var a = 10;
var b = 10;
var c = 30;
var d = 30;
if ((a === b) && (c === d)) {
console.log("a
is equal to be and c is equal to d");
}
</script>
</body>
</html>
The above example uses double „&“, which means
„and“.
What if we are interested one OR the other situation.
If the variable a is strictly equal to be OR if the variable c is strictly
equal to d. We use the double vertical bar.
Example:
<html>
<head>
<title>Untitled Document</title>
</head>
<body>
<div id="demo">
<h1>This is a heading.</h1>
<p>This is a paragraph.</p>
</div>
<script>
var a = 10;
var b = 10;
var c = "30";
var d = 30;
if ((a === b) || (c === d)) {
console.log("The
code block will be executed even if one of the conditions return true.");
}
</script>
</body>
</html>
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