Comments

Users can insert comments anywhere in a script. Comments are not executed like regular code. Instead, they can be used for documentation or to temporarily disable blocks of code.

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indicates that the result of the expression 1 + 2 is 3.

Calling Functions

A function takes in some parameters and returns a value. This lets you re-use pieces of code without re-writing everything.

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For example, tag.write takes two arguments. The first argument is the tag name, and the second argument is the value to write:

tag.write("my_tagmyTag", true); writes the value true to the tag named "my_tagmyTag"

Declaring Variables

Variables let you store values and access them later in the script.

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Variables can be declared using the following format:

var variable_namevariableName;

To declare more than one variable, use a comma , between each variables:

var variable_name_1, variable_name_2variable1, variable2, ... , variable_name_nvariablen;

Users can also define an initial value for the variable when declaring it using the following format:

var variable_name variableName = 1;

If you do not specify an initial value, then the variable’s value is undefined.

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Using and Setting Variables

Once a variable has been declared, you can assign a new value to it using the assignment operator =. For example:

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var tag_name = "my_tagmyTag";
var value = 1;
tag.write(tag_nametagName, value);

This is the same as:

tag.write("my_tagmyTag", 1);

Operators, Expressions, and Parentheses

You can add, subtract, multiply, and use other operators on variables and other values. See the “Operators” section for more information.

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You may also nest function calls:

tag.write("my_tagmyTag", !tag.read("my_tagmyTag")) // toggles the value of the tag named "my_tagmyTag"

It is worth noting that the comparison operator == is different from the assignment operator =. The comparison operator == compares two values and returns true if they are equal, and returns false if they are not equal. The assignment operator = sets the variable on the left side to the value on the right side, and always returns assigned value. For example:

var x = 3;
x == 5; // false (because 3 does not equal 5)
x = 5;  // 5 (because 5 is the value being assigned)
x == 5; // true (because we set x to 5 in the line above)

Data Types

In JavaScript, every expression and variable has a data type. The most basic types are Boolean, Number, and String, which can be used to read and write tag values.

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var x = 3;
typeof x; // "number"

Strings, Quotes, and Escape Characters

Anything wrapped in either double quotes " or single quotes ' will be treated as a string value. For example, x without quotes would refer to the variable x. But "x" or 'x' would be a string with the value "x". For example:

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"Line 1\nLine 2"; // Line 1
                  // Line 2
"1\t2\t3";         // 1   2   3

Reading and Writing Tag Values

To get a tag’s current value, use tag.read. This function has one argument, which is the name of the tag, and returns the tag’s value.

var my_valmyVal = tag.read(“my_tag““myTag“); // assigns the value of the tag "my_tagmyTag" to the variable my_valmyVal

To write set a tag tag’s value, use tag.write. This takes in two arguments: (1) the name of the tag and (2) the value to write. tag. write always returns undefined.

tag.write(“my_tag”“myTag”, 1); // writes the value 1 to the tag "my_tagmyTag"

Tags within in tag groups can be accessed using the / character. For example:

tag.write("outer_group/inner_group/my_tagouterGroup/innerGroup/myTag", 1);

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Note that tag.read and tag.write do not bind the tag to a variable. For example, consider the following script:

var value = tag.read("myTag");
// do some stuff that takes a long time
value = value + 1;

This would not affect the tag “myTag”, and value on line 3 might not be using the most recent tag value.

Each time you want to get the most recent tag value, you must use tag.read, and each time you want to write to the tag, you must use tag.write. To fix the example above:

var value = tag.read("myTag");
// do some stuff that takes a long time
value = tag.read("myTag"); // get the most recent tag value
value = value + 1;
tag.write("myTag", value); // write the script value to the tag

Semicolons

JavaScript uses semicolons to indicate the end of expressions. Using semicolons at the end of lines is not required, but is recommended for better organization and clarity:

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some_function();some_other_function;

Whitespace

JavaScript ignores whitespace characters like spaces, tabs, and line breaks.

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