jscommand

Command pattern for JavaScript

$3

To create a command, create a class that inherits from Command.
``cs
class Add extends Command
{
constructor(private a:number)
{
super();
}

action(data:any): any
{
return data + this.a;
}
}

let command = new Add(3);
await command.execute(2); //Return 5
`

$3

A command can be executed conditionally by using IfCommand.

`cs
await new IfCommand(false, new Add(2)).execute(1); // Returns undefined
await new IfCommand(true, new Add(2)).execute(1); // Returns 3
`

$3

Commands can be chained and executed in as a single unit by using MacroCommand.

`cs
let commands = new MacroCommand();
commands.add(new Add(3));
commands.add(new Add(4));
commands.add(new Add(5));

await commands.execute(0); //Returns 12
`

$3

A command can be rolled back if it inherits from RevertableCommand.

`cs
class Add extends RevertableCommand
{
constructor(private a:number)
{
super();
}

action(data:any): any
{
if(data > 2) throw new Error('Overflow!')
return data + this.a;
}

revert(data:any): any
{
console.log('Rollback')
}
}

let commands = new RevertableMacroCommand();
commands.add(new Add(1));
commands.add(new Add(1));
commands.add(new Add(1));
commands.add(new Add(1));

await commands.execute(0);

`

$3

A command execution can be logged by wrapping the command with TraceableCommand

`cs

new TraceableCommand(new Add(3)).execute(1); //Returns 4 and execution information is logged to console.

`

$3

To supporess an error from a command, wrap the command with FailSafeCommand

`cs
new FailSafeCommmand(new CouldThrowAnErrorCommand()).execute();
`

$3

A command can be retried if an expected error occurs if the command is wrapped with RetryableCommand.

`cs
new RetryableCommand(new Add(3), Error, 3).execute(0); //The command Add() will be executed. If an error of type Error occurs, Add() will be re-executed 3 more times.
`

$3

A sleep command sets a ranom timeout between to millisecond valuesCommands can be chained to perform complex operations.

`cs
let minMsWait = 50; // 50 milliseconds
let maxMsWait = 1500; // 1500 milliseconds
new SleepCommand(minMsWait, maxMsWait).execute(0);
`

$3

For simplicity, AnonymousCommand can be used to wrap a function so that a function can act as a command.

`cs
let command = new AnonymousCommand((a)=>a+1);
await command.execute(2); //Returns 3
`

$3

Commands can be chained to perform complex operations.

`cs
let commands = new MacroCommand();
commands.add(new IfCommand(new AnonymousCommand((a)=>a+1 > 2), new Add(1));
commands.add(new RetryableCommand(new Add(2)));

new TraceableCommand(commands).execute(0);
`

$3

A OneOf command executes the given commands in order and will return once
a command executed successfully. The remaining commands will not be executed.

`cs
let commands = new OneOfCommand();
commands.add(new DoSomeThingCommand());
commands.add(new TryThisIfTheFirstCommandFailed()));
commands.add(new TryThisIfTheSecondCommandFailed()));

new TraceableCommand(commands).execute();
``