Arithmetic Operators : +, -, *, /
In JavaScript, arithmetic operators take numerical values (either literals or variables) as their operands and return a single numerical value. There are four standard arithmetic operators, addition (+), subtraction (-), multiplication (*), and division (/).
These operators work as they do in other programming languages except the division (/) operator which returns a floating-point division in JavaScript, not a truncated division as it does in languages such as C or Java.
For example:
1/2 returns 0.5 in JavaScript.
1/2 returns 0 in Java.
In addition, JavaScript provides modules(%), increment(++), decrement(--) and unary negation(-) operators.
+ addition operator
HTML Code
<!doctype html> <head> <meta charset="utf-8"> <title>JavaScript + operator example</title> <meta name="description" content="This document contains an example of JavaScript + operator" /> </head> <body> <script src="addition_example1.js"></script> </body> </html>
JS Code
var var1 = 45;
var var2 = 78;
var var3 = 45.10;
var var4 = 178.12;
var newvar = var1 + var2;
var newvar1 = var3 + var4;
var newParagraph3 = document.createElement("p");
var newText3 = document.createTextNode("var1 + var2 = "+newvar+" and var3 + var4 = "+newvar1);
newParagraph3.appendChild(newText3);
document.body.appendChild(newParagraph3);
- subtraction operator
HTML Code
<!doctype html> <head> <meta charset="utf-8"> <title>JavaScript subtraction operator example </title> <meta name="description" content="This document contains an example Using JavaScript subtraction operator"/> </head> <script src="subtraction-example1.js"></script> </body> </html>
JS Code
var var1 = 45;
var var2 = 78;
var str1 = "w3resource";
var str2 = ".com";
var newvar = var1 - var2;
var newstr = str1 - str2; //NAN
var varstr = var1 - str2; //NAN
var newParagraph = document.createElement("p");
var newText = document.createTextNode("var1 -var2 = "+ newvar);
newParagraph.appendChild(newText);
document.body.appendChild(newParagraph);
var newParagraph1 = document.createElement("p");
var newText1 = document.createTextNode("str1 - str2 = "+ newstr);
newParagraph1.appendChild(newText1);
document.body.appendChild(newParagraph1);
var newParagraph2 = document.createElement("p");
var newText2 = document.createTextNode("var1 - str2 = "+ varstr);
newParagraph2.appendChild(newText2);
document.body.appendChild(newParagraph2)
* multiplication operator
HTML Code
<!doctype html><head> <meta charset="utf-8"> <title>JavaScript multiplication operator (*) example with DOM </title> <meta name="description" content="This document contains an example Using JavaScript multiplication operator (*) with dom"/> </head> <body> <script src="multiplication-example1.js"></script> </body> </html>
JS Code
var var1 = 45;
var var2 = 78;
var var3 = 45.10;
var var4 = 178.12;
var newvar = var1 * var2;
var newvar1 = var3 * var4;
var newParagraph = document.createElement("p");
var newText = document.createTextNode("var1 * var2 = "+ newvar);
newParagraph.appendChild(newText);
document.body.appendChild(newParagraph);
var newParagraph1 = document.createElement("p");
var newText1 = document.createTextNode("var3 * var4 = "+ newvar1);
newParagraph1.appendChild newText1);
document.body.appendChild(newParagraph1);
/ division operator
HTML Code
<!doctype html> <head> <meta charset="utf-8"> <title>JavaScript / operator example </title> <meta name="description" content="This document contains an example of JavaScript division operator" /> </style> </head> <body> <script src="division-example1.js"></script> </body> </html>
JS Code
var var1 = 45;
var var2 = 78;
var var3 = 1;
var var4 = 2;
var newvar = var1 / var2; //0.5769230769230769
var newvar1 = var3 / var4; //0.5
var newParagraph = document.createElement("p");
var newText = document.createTextNode ("var1 / var2 = "+ newvar);
newParagraph.appendChild(newText);
document.body.appendChild(newParagraph);
var newParagraph1 = document.createElement("p");
var newText1 = document.createTextNode("var3 / var4 = "+ newvar1);
newParagraph1.appendChild(newText1);
document.body.appendChild(newParagraph1);
Arithmetic Special Operators (%, ++, --, - )
Assignment Operators(+=,-=,*=,/=,%=,<<=,>>=,>>>=,&=,^=,|=)
Bitwise Operators(a & b,a | b,a ^ b,~ a,a << b,a >> b,a >>> b)
Comparison Operators(==,===,!=,!==,>,>=,<,<=)
Equal (==)
x == y Returns true if the operands are equal.
var s1 = 300; var s2 = '300'; alert(s1==s2);//true
Strict equal (===)
x === y Returns true if the operands are equal and of the same type.
var s1 = 300,
s2 = '300',
s3 = 300;
alert(s1===s2);//false
alert(s1===s3);//true
Not equal (!=)
x != y Returns true if the operands are not equal.
var s1 = 300, s2 = '300', s3 = 500; alert(s1!=s2);//false alert(s1!=s3);//true
Strict not equal (!==)
x !== y Returns true if the operands are not equal and/or not of the same type.
var s1 = 300, s2 = '300', s3 = 500; alert(s1!==s2);//true alert(s1!==s3);//true
Greater than (>)
Greater than or equal (>=)
Less than (<)
Less than or equal (<=)
Logical Operators(&&, ||, !)
String Concatenation(+, +=)
Special Operators:
?: (Conditional operator)
Condition ? expr1 : expr2
status = (marks >= 30) ? "Pass" : "Fail"
Comma Operator
The comma operator (,) is used to execute two expressions sequentially.
expr1, expr2
We use the comma operator when we want to include multiple expressions in a location that requires a single expression.
This operator is generally used inside a for loop, to allow multiple variables to be updated (increase/decrease) each time through the loop.
For example we want to display a serial No. (starting from 1) and a employee code ( starting from 10 ), the following code uses the comma operator to increment two variables at once.
for (var i=1, j=10; i <=10; i++, j++)
{
alert('Sl. No. : '+i+' Employee Code : '+j)
}
function Operator
The function operator defines a function inside an expression.
var1 = function( parameter1, parameter2,......parametern)
{
statement(s)
}
var a = 12;
var b = 14;
var x = function(a,b)
{
return a*a+2*a*b+b*b;
};
alert("The square of "+a+ " and "+b +" is " +x(a,b));
in Operator
property in object
判断某个属性是否在对象中存在
property : Name of the property.
object : Name of the object.
var employeeobj = {name:"Robert",designation:"Officer",age:"34"};
if ("designation" in employeeobj)
{
alert('Designation property is present'); //alert this
}
else
{
alert('Designation property is not present');
}
instanceof Operator
The instanceof operator is used to check the type of an object at run time. The instanceof operator returns a boolean value that indicates if an object is an instance of a particular class.
var result = objectName instanceof objectType
var string1 = "w3resource"; //Declaring string object
var date1 = new Date(); //Declaring Date object
if (string1 instanceof String)
{
var newParagraph = document.createElement("p");
var newText = document.createTextNode('The type of string1 object is String');
newParagraph.appendChild(newText);
document.body.appendChild(newParagraph);
}
if (date1 instanceof Date)
{
var newParagraph1 = document.createElement("p");
var newText1 = document.createTextNode('The type of date1 object is Date');
newParagraph1.appendChild(newText1);
document.body.appendChild(newParagraph1);
}
new Operator
The new operator is used to create an instance of a user defined object type or one of builtin object types which has a constructor function.
var objectName = new objectType(param1, param2, ...., paramN);
To create an user defined object type following steps are required.
Write a function to define the object type 写一个函数来定义一个对象类型
Use new operator to create an instance of the object. 使用new操作符创建这个对象的实例
Suppose we want to create an object type for students with three properties name, class and rollno. To do this first declare the following function.
function student(name, class, rollno)
{
this.name = name;
this.class = class
this.rollno = rollno;
}
使用new关键字完成对象的创建
studentv = new student("John", "V", 10)
studentvi = new student("David Rayy", "VI", 12)
function school(sname, city, stus)
{
this.sname = sname;
this.city = city;
this.stus = stus;
}
var stus = new Array(studentv,studentvi);
school = new school("Dubai International School", "Dubai", stus);
this Operator
The this operator is used to refer the current object. In general, this refers to the calling object in a method.
In the following web document this operator is used as internal reference property of the form instances.
<!doctype html> <head> <meta charset="utf-8"> <title>JavaScript this operator example with DOM </title> <meta name="description" content="This document contains an example of JavaScript this operator"/> </head> <body> <form name="myform" action="#"> <input type="text" value="Text Here" name="text1" /> <input type= "submit" value="Submit" name="mysubmit" onclick= "formdetails(this.form)" /> </form> <script src="javascript-this-operator-example1.js"> </script> </body> </html>
//this ---> form
function formdetails(form)
{
var newParagraph = document.createElement("p");
var newText = document.createTextNode("The name of the form is: "+form.name);
newParagraph.appendChild(newText);
document.body.appendChild(newParagraph);
var newParagraph1 = document.createElement("p");
var newText1 = document.createTextNode("The
deault value of text box is: "+form.text1.value); newParagraph1.appendChild(newText1);
document.body.appendChild(newParagraph1);
var newParagraph2 = document.createElement("p");
var newText2 = document.createTextNode("The name
of the submit button box is: "+form.mysubmit.name); newParagraph2.appendChild(newText2);
document.body.appendChild(newParagraph2);
var newParagraph3 = document.createElement("p");
var newText3 = document.createTextNode("The deault
value of submit button is: "+form.mysubmit.value);
newParagraph3.appendChild(newText3);
document.body.appendChild(newParagraph3);
}
typeof operator
The typeof operator is used to get the data type (returns a string) of its operand.
The operand can be either a literal or a data structure such as a variable, a function, or an object. The operator returns the data type.
返回值：字符串
"object"，"boolean"，"function"，"number"，"string"，"undefined"
Examples of typeof operator : string
typeof "" typeof "abc" typeof (typeof 1)
Examples of typeof operator : number
typeof 17 typeof -14.56 typeof 4E-3 typeof Infinity typeof Math.LN2 typeof NaN
Examples of typeof operator : boolean
typeof false typeof true
Examples of typeof operator : function
typeof Math.tan
typeof function(){}
Examples of typeof operator : object
typeof {a:1}
typeof new Date()
typeof null
typeof /a-z/
typeof Math
typeof JSON
Examples of typeof operator : undefined
typeof undefined typeof abc
More examples on typeof operator
typeof(4+7); //returns number typeof("4"+"7"); //returns string typeof(4*"7"); //returns number
typeof(4+"7"); //returns string
What is the difference between typeof myvar and typeof(myvar) in JavaScript?
No difference!
How to detect an undefined object property in JavaScript?
var index = 8; var result = (typeof index === 'number'); alert(result); // Output: true var description = "w3resource"; var result = (typeof description === 'string'); alert(result); // Output: true
void operator
The void operator is used to evaluate a JavaScript expression without returning a value.
The following web document shows how the void operator is used.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset=utf-8>
<title>JavaScript void operator example</title>
</head>
<body>
<a href="javascript:void(alert('Thank you.'))">Click here to see a message</a>
</body>
</html>
In the following web document void operator is used to call a function.
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset=utf-8>
<title>JavaScript void operator (calling function) example</title>
</head>
<body>
<script type="text/javascript">
function testfunc(){document.write("good!");}
</script>
<a href="javascript:void(testfunc())">
Click here to call testfunc()</a>
</body>
</html>