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# Variables 2

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### Variables 2

1. 1. JavaScript Variables, Function and Method Parse a value (parseFloat and parseInt) Round method(Math.round)
2. 2. Checking the Assignment• Using JavaScript write the source code using prompt box , alert box and document.write.1. Converts the user-specified temperature reading ina. Fahrenheit to CelsiusF= ?C= (F-32)* 5/9b. Celsius to KelvinC= ?K= C + 273.15
3. 3. <html><body><script>var F= 25var C= (F-32)*5/9alert(""+C+"")document.write(""+C+"");document.write("",parseInt(C));</script><script>var fahrenheit= parseFloat(prompt("Enter Fahrenheit "," "));var celsius= (fahrenheit-32)*5/9alert(""+celsius+"");document.write(""+celsius+"");document.write("",parseInt(celsius));</script>
4. 4. • <script>• var C= 25• var K= C + 273.15• alert(""+K+"");• document.write(""+K+"");• </script>• <script>• var celsius= parseFloat(prompt("Enter Celsius "," "));• var kelvin= celsius + 273.15• alert(""+kelvin+"");• document.write(""+kelvin+"");
5. 5. • <html>• <body>• <script>• var name= prompt("Enter your name "," ");• var school= prompt("Enter your school "," ");• var yearlevel= prompt("Enter your year level "," ");• var section= prompt("Enter your section "," ");• document.write(""+name+"" + "<br>");• document.write(""+school+"" + "<br>");• document.write(""+yearlevel+"" + "<br>");• document.write(""+section+"" + "<br>");• </script>• </body>• </html>
6. 6. JavaScript Variables• As with algebra, JavaScript variables can be used to hold values (x=5) or expressions (z=x+y).• Variable can have short names (like x and y) or more descriptive names (age, sum, totalvolume).• Variable names must begin with a letter• Variable names can also begin with \$ and _ (but we will not use it)• Variable names are case sensitive (y and Y are different variables)• Both JavaScript statements and JavaScript variables are case-sensitive.
7. 7. JavaScript Data Types• JavaScript variables can also hold other types of data, like text values (name="John Doe").• In JavaScript a text like "John Doe" is called a string.• There are many types of JavaScript variables, but for now, just think of numbers and strings.• When you assign a text value to a variable, put double or single quotes around the value.• When you assign a numeric value to a variable, do not put quotes around the value. If you put quotes around a numeric value, it will be treated as text.• Example var pi=3.14; var name="John Doe"; var answer=Yes I am!;
8. 8. One Statement, Many Variables• You can declare many variables in one statement. Just start the statement with var and separate the variables by comma:• var name="Doe", age=30, job="carpenter";• Your declaration can also span multiple lines:• var name="Doe", age=30, job="carpenter";
9. 9. JavaScript parseInt() Function• Definition and Usage--------The parseInt() function parses a string and returns an integer.• Note: Only the first number in the string is returned!• Note: Leading and trailing spaces are allowed.• Note: If the first character cannot be converted to a number, parseInt() returns NaN.
10. 10. EXAMPLE OUTPUT<script>document.write(parseInt("10") + "<br>"); 10document.write(parseInt("10.33") + "<br>"); 10document.write(parseInt("34 45 66") + "<br>"); 34document.write(parseInt(" 60 ") + "<br>"); 60document.write(parseInt("40 years") + "<br>"); 40document.write(parseInt("He was 40") + "<br>"); NaN</script>
11. 11. JavaScript round() MethodDefinition and Usage• The round() method rounds a number to the nearest integer.Syntax Methodvar x= Math.round(10.53)var y= Math.round(8/5) Value to be rounded offvar z= Math.round(mass/volume)
12. 12. More ExamplesExample OUTPUTvar a=Math.round(2.60); 3var b=Math.round(2.50); 3var c=Math.round(2.49); 2var d=Math.round(-2.60); -3var e=Math.round(-2.50); -2var f=Math.round(-2.49); -2