jberryman/dilly.js

a silly library for loops with delays in JavaScript.

dilly.js is a silly lib for loops with delays in JavaScript.

Motivation

We might be implementing a game or simulation and want to write our code as one or several nested loops, with a delay on the inner loop like

while (playing) {
    update_monsters();
    update_display();
    sleep 10;
}
exit_stuff();

...but JavaScript only provides the non-blocking setTimeout which necessitates an inversion of control and makes our simple algorithm clumsy to write and very difficult to read.

I wanted this while implementing this.

Usage

We provide the single function withDelay, and things work functionally- similar to jQuery or list comprehensions. Here are some examples:

Examples

A simple "while" game loop that gets progressively faster. When done, the script continues with exit_stuff().

// "while" is passed a predicate that returns a Bool, so
var b = true,
    playing = function(){ return b };

withDelay(100).endingWith(exit_stuff)
    .while(playing)
        .do(function(){
            update_monsters();
            update_display();
    
            var d = this.delay();
            this.delay(d-1);
        })

Nested "foreach" and "forRange" style loops, running with no delay and without any explicit continuation (i.e. control is immediately passed to other_stuff while the loop continues running in the background).

Range/step loop behavior esoterica should follow ruby's behavior.

withDelay()
    .for("x",1,2)                // range: 1, 2
        .for("y",1,3 , 8)        // range(with step of 2): 1, 3, 5, 7
            .for("z",['a','b'])  // foreach: 'a', 'b'
                .do(function(){ 
                    console.log(this.var("x"), 
                                this.var("y"), 
                                this.var("z"));
                 });
other_stuff;

A list comprehension-style guard function:

withDelay(1000).endingWith( function(){console.log("done")} )
    .for("x",1,5)               
        .for("y",[1,2,3,4,5])
            // filter parent loop iterations where `x+y == 5`
            .guard(function(){
                    return (this.var("x") + this.var("y")) === 5})
                .do(function(){ 
                    console.log(this.var("x"), this.var("y")) 
                    // OUTPUTS: (1,4)... (2,3)... (3,2)... (4,1)... "done" 
                 })

Limitations and caveats

• delays only happen after each iteration of the inner do block
• we can't interleave bits of code before or after a nested child loop (again what we're doing is closer in spirit to list comprehensions than proper loops)
• dictionary of "bound" names works in braindead fashion, "scoping" might be strange
• no implementation for break/continue; see if you can do what you need with guard

Please see the code for the true story and submit pull-requests to help improve documentation or add/adjust functionality if you find this useful.

dilly.js's Issues

[i]?

https://discordapp.com/channels/103547166454198272/154847587973857280

var unreadChannels = $('.channel.channel-text.unread');
withDelay(1000).endingWith( function(){console.info("done")} )
    .for(unreadChannels,1,unreadChannels.length)
        .do(function(){ 
            $(unreadChannels).find('.channel-name').click();
        });