**Attaching an External Script**

The advantage is that you have 1 file that effects multiple pages, this makes editing easier.

1. The extension has to be .js

2. you add src:

<script type="text/javascript" src="myExternal.js"></script>

3. make sure there is nothing between the <script> tags

The order that you attach scripts is important.

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**Trouble Shooting**

Unfortunately the browsers interpret the scripts differently. The different browsers have tools to help you figure out errors.

**Firefox:**

Tools >> Error Console

Usually the information presented by the console is useless, but it gives you an idea of the area that is probably causing problems.

**Firebug:**

More usefull

**Webdeveloper: (just for Firefox)**

A toolbar extension that is really helpful, in particular with jQuery.

**Safari:**

Develop >>> Show Error Console

--------------------------REVIEW of the READING ASSIGNMENT-------------------------

**Operators**

Operators are Symbols that allow us to manipulate/modify data.

= assignment operator

(set to the value of)

**Math Operators**

+ - * /

PEMDAS aka Please Excuse My Dear Aunt Sally

Parenthesis

Exponents

Multiplication

Division

Addition

Subtraction

M and D have the same weight

A and S have the same weight

so these are performed left to right

(PEMDAS

--------------

Concatenation

+ the operator use to concatenate

(this is not the same as the mathematical operator + )

var lastName = "Fartyfatkins";

var firstName = "Hugo";

var theName = firstName + ' ' + lastName;

document.write(theName);

The Point this is to show that you should not have the ' ' (space) in the variable declaration.

var lastName = "Fartyfatkins "; BAD

Fixing -

Number(variable) +Number(variable2)

-------------------------------------

**Order of operations:**PEMDAS aka Please Excuse My Dear Aunt Sally

Parenthesis

Exponents

Multiplication

Division

Addition

Subtraction

M and D have the same weight

A and S have the same weight

so these are performed left to right

(PEMDAS

**will**be on the test)--------------

**Combining Strings**Concatenation

+ the operator use to concatenate

(this is not the same as the mathematical operator + )

var lastName = "Fartyfatkins";

var firstName = "Hugo";

var theName = firstName + ' ' + lastName;

document.write(theName);

The Point this is to show that you should not have the ' ' (space) in the variable declaration.

var lastName = "Fartyfatkins "; BAD

Fixing -

**Automatic Type Conversion**Number(variable) +Number(variable2)

**Changing the Values in Variables**

score = 0;

score = score + 3;

The point is that everything that happens on the right, gets dumped into the left.

-------------------------------------

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