c12012oct914.notebook october 09, 2014cisweb.bristolcc.edu/.../cis120/c12012oct914.pdf · 2014. 10....

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Our first JavaScript program.

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Right click and select View Page Source to see the code that made this page.

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The JavaScript is inside html. I didminimum html so we could focus onJavaScript.

I tell the browser that I am going tostart using JavaScript by usingthe script tag.

I am doing the write method on the document. So, I am writing the contents of the parenthesis.I am writing the literal Hello World! which because it is a literal is enclosed in quotes.

alert() will put the literalHello World! in the prompt.

Note that each of the JavaScript code lines ends in a semi­colon.The semi­colon means that instructor is done.

Note that the script has a .html extension.

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The next JavaScript, multiply.html will ask the user to input two numbers. The user types one number, clicks OK and will then be prompted for the next number.

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Next it will prompt for the second number.

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67

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Here the write will put out the literal followed by the number stored in the variable ans.Note that I left a space after is so there would be a space between the literal and the 24.

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parseFloat deals with decimal numbers and parseInt deals with integers.

parseFloat specifies thatfirstnum and secondnumwill be numbers so the + causes an ADD to happen.

Here firstnum andsecondnum areconcatenatedto make 83.

document.write("<br>"); has a literal <br> and that literal is a tag so a line is skipped.

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Data comes in a text or string. If I add I want numbers. I usethings like parseFloat to convert from text to number format sowe can use the data in a calculation.

I can also use + or Numberto convert.

parseFloat allows for decimalsparseInt allows for whole numbers

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When I calculate and assign to a variable ortake in data and assignto a variable, I use =.

When I compare forequality I use ==.

What to do if the condition is true is enclosed in curly braces.After the else, you enclose what to do if the condition is false in curly braces.

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"" means that a field is empty or null.condition is in parenthesis

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What happens if I enter something other than or * or /. As we saw, if I enter a + or a B or a 5you will take the else and do the divide.

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Now if the user does not enter an *, I check to see if they entered a /. If that is not true then I decided to move 0 to ans. I could have also put out an errormessage.

Next I need to put this in the JavaScript code.

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The else is now going to ask the second question. The second question is whether wanttodo == /. If it does I will do a divide,if it does not I will set ans = 0.

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The else is now going to ask the second question. The second question is whether wanttodo == /. If it does I will do a divide,if it does not I will set ans = 0.

Note after the else I have two curly braces and embedded inside themI ask the next question and deal with its yes and its no.

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Need to add the + and ­

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Now I want to deal with + ­ as well as * /

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