VirtualMV/JavaScript/Starting/Operators

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Introduction

Overview

VmvIcon Objectives.png

By the end of this page you will be able to:

  • Describe common operators in JavaScript

Operators

Arithmetic operators

Operator Description Example Result
+ Addition var intNum = 2+2; 4
- Subtraction var intNum = 5-2; 3
* Multiplication var intNum = 4*5; 20
/ Division var intNum=15/5;
var
3
% Modulus (remainder after division) var intNum = 5%2;
var intNum = 10%8;
1
2
++ Increment var intX=5;
intX++;
intX=6
-- Decrement intX=3;
intX--;
intX=2

Comparison Operators

Operator Description Example
== is equal to 4==8 returns false
!= is not equal 4!=8 returns true
> is greater than 4>8 returns false
< is less than 4<8 returns true
>= is greater than or equal to 4>=8 returns false
<= is less than or equal to 4<=8 returns true

Logical Operators

Operator Description Example
&& and

x=5;
y=4;
(x<10 &&y>1) returns true

|| or x=6;
y=3;
(x==5|| y==7) returns false
! not x=6;
y=4;
x != y returns true;

---

3 logicians walk into a cafe. The waiter asks "do you ALL want a drink?"

The first says "I don't know", the second says "I don't know" the third says "Yes please"

Conditional Operators

JavaScript also contains a conditional operator that assigns a value to a variable based on some condition. JavaScript Comparison and Logical Operators (W3Schools)

Examples

The following code shows that JavaScript allows for some quite sophisticated assignments.

//This allows you to change a greeting based on the contents of the txtVisitor variable
//if the visitor = PRES then put Dear President otherwise just Dear
 
var txtGreeting=(txtVisitor=="PRES")?"Dear President ":"Dear ";
 
// Here a date object is created. 
// If d is < 10 then a zero is added to the front else just leave d as is.
var date = new Date();
var d  = date.getDate();
var day = (parseInt(d) < 10) ? '0' + d : d;

Example (js1_05)

<html>
<body>
<script type="text/javascript">
  var intA = 3;
  var intB = 5;
  var intSum = intA + intB;
  var intProd = intA * intB;
  document.write("The sum of 3 and 5 is " + intSum +"<br />");
  document.write("The product of 3 and 5 is " + intProd);
</script>
<p>This example declares some variables, assigns values to them,
performs a calculation and then displays the results.</p>
</body>
</html>

Example :Click here to run js1_05.

Note that in the example the variables are assigned numbers. If you accept values from a prompt or a text box (from a form) the "numbers" are actually text so need to be converted if you want to do arithmetic operations on them.


VmvIcon References.png References

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VirtualMV/JavaScript/Starting/Operators. (2017). In WikiEducator/VirtualMV wiki. Retrieved October 18, 2017, from http://wikieducator.org/VirtualMV/JavaScript/Starting/Operators    (zotero)