View source for Tutorial/Scripting

{{ambox|type=note|text=This tutorial is incomplete}}

Knotter has a script engine that can be used to automate tasks and provide new tools.
This tutorial shows how to execute simple scripts and to create a plugin.

==Introduction==
To execute simple code snippets you can use the [[Manual/Dialogs/Script Console|script console]], which can be toggled via {{app menu|View > Dialogs > Script Console}}.
From there, you can type your line at the bottom and hit enter to execute it.

The scripting language used by Knotter is [http://qt-project.org/doc/qt-5.0/qtscript/ecmascript.html ECMAScript]. This section gives a minimal introduction to the language, if you are already familiar with the language you can skip it.

===Hello World===
Let's start with a classical example, the Hello World program:
{{js_example|print("Hello World")|output=Hello World}}
Here {{js|print}} is one of the built-in functions; {{"Hello World"}} is a string literal, passed as an argument to that function.

The {{js|print}} function writes its arguments to the script console. If multiple arguments are passed, each one is written, separated by a space character.
{{js_example|print("Hello", 'World')|output=Hello World}}

===Variables and values===
Expressions can yield a value, for example {{js|5+3}} results in {{js|8}}.

It's often useful to assign a name to a value to be able to retrieve it quickly later on. To do this we can use variables. A value can be copied to a variable using an assignment expression:
{{js example|a {{=}} 2 + 3|output=5}}
Here the expression {{js|2+3}} is evaluated and the result ({{js|5}}) is copied to the variable {{a}}. Any previous value of {{a}} is discarded.