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

Declaring Variables

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

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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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tag.write("myTag", 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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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.

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

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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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