Decree JS allows you to execute a function when a specified key sequence is pressed. To register a key sequence with Decree JS, you use the decree.when method.

The decree.when method takes in one argument, which is a string consisting of one key. The argument can be almost any key on the keyboard. See the full list of supported keys. This method starts the definition of the key sequence you want to register with Decree JS.

To continue the key sequence definition, you have to chain off of the returned value from decree.when. Three methods are available to chain off of decree.when:

• then
• withModifier
• withModifiers
• perform

The decree.when, then, and withModifier methods all take the same single argument, and all are chainable with the same three methods plus withModifiers returned by decree.when. These three methods are how you define the sequence of key presses you want to Decree JS to listen for.

The perform method also takes a single argument, a function to be called when Decree JS notices that the key sequence you registered is pressed while the browser is in focus. Calling this method ends the key sequence you are registering. It returns a function that can be called to deregister the just registered key sequence.

The then method will register a sequential key press that comes after the key given to the previous method. So if you execute decree.when('a').then('b'), you need to press and release the a key, and then press and release the b key for Decree JS to match your registered decree with keys pressed in the browser.

The withModifier method attaches a modifier key to the previously defined key. A modifier key must be pressed before the key it is attached to. So if you execute decree.when('a').withModifier('b'), you need to press and hold the b key, and then press and release the a key. You'll also need to release the modifier key before the next part of the key sequence, if one exists. You can release the modifier key or the main key in any order. If the then method is called after the withModifier method, it starts a new sequential state that doesn't expect the previous modifier key to be held down.

The withModifiers method is for when you have multiple modifiers for a single key sequence. It takes in the list of modifiers for the previously defined key as individual arguments to the function. It also acts a convenicence method that replaces the need for chaining multiple withModifier calls.

An object containing the methods then, withModifier, withModifiers, and perform.

An object containing the methods then, withModifier, withModifiers, and perform.

An object containing the methods then, withModifier, withModifiers, and perform.

An object containing the methods then, withModifier, withModifiers, and perform.

A deregistration function for the just registered key sequence.

decree.when('a').perform(function() {
    console.log('"a" was pressed and released.');
});

decree.when('a').then('s').perform(function() {
    console.log('"a" was pressed and released, then "s" was pressed and released');
});

decree.when('a').withModifier('b').perform(function() {
    console.log('"b" was pressed and held, then "a" was pressed and released.');
});

decree.when('a').withModifiers('b', 'c').perform(function() {
    console.log('"b" and "c" were both pressed and held (in any order), then "a" was pressed and released.');
});

decree.when('q').withModifier('a').then('w').withModifier('s').perform(function() {
    console.log('"a" was pressed and held, then "q" was pressed and released, then "a" was released". Then, "s" was 
    pressed and held, then "w" was pressed and released, then "s" was released.');
});

var deregistrationFn = decree.when('x').then('y').perform(function() {
    console.log('this will execute only up until the deregistration function is called');
});
deregistrationFn();

You can configure Decree JS by calling the decree.config method. This method takes one parameter, a JSON object. The list of configurable properties, along with their defaults, is shown below in the sample code:

decree.config({
   timeThreshold: 500      //the time Decree JS waits between key presses to continue the current key sequence
                           //this property is in milliseconds
});

These are the strings that the decree.when, then, and withModifier methods can take as a parameter.

• "space"
• "enter"
• "return"
• "tab"
• "esc"
• "escape"
• "backspace"
• "shift"
• "control"
• "ctrl"
• "alt"
• "0"
• "1"
• "2"
• "3"
• "4"
• "5"
• "6"
• "7"
• "8"
• "9"
• "left"
• "up"
• "right"
• "down"
• "a"
• "b"
• "c"
• "d"
• "e"
• "f"
• "g"
• "h"
• "i"
• "j"
• "k"
• "l"
• "m"
• "n"
• "o"
• "p"
• "q"
• "r"
• "s"
• "t"
• "u"
• "v"
• "w"
• "x"
• "y"
• "z"