define a function for each array element

Question

I want to do this without writing the code X times. How you do that in JavaScript ? I am from Java.

        floors[0].on("up_button_pressed", function() { 
            elevator.goToFloor(floors[0].floorNum());
        } );
        floors[0].on("down_button_pressed", function() { 
            elevator.goToFloor(floors[0].floorNum());
        } );

        floors[1].on("up_button_pressed", function() { 
            elevator.goToFloor(floors[1].floorNum());
        } );
        floors[1].on("down_button_pressed", function() { 
            elevator.goToFloor(floors[1].floorNum());
        } );

        floors[2].on("up_button_pressed", function() { 
            elevator.goToFloor(floors[2].floorNum());
        } );
        floors[2].on("down_button_pressed", function() { 
            elevator.goToFloor(floors[2].floorNum());
        } );        

        floors[3].on("up_button_pressed", function() { 
            elevator.goToFloor(floors[3].floorNum());
        } );
        floors[3].on("down_button_pressed", function() { 
            elevator.goToFloor(floors[3].floorNum());
        } ); 

        floors[4].on("up_button_pressed", function() { 
            elevator.goToFloor(floors[4].floorNum());
        } );
        floors[4].on("down_button_pressed", function() { 
            elevator.goToFloor(floors[4].floorNum());
        } );

Why does every individual floor have its own on event? There should be one event listener and the event should contain the information which button was pressed on which floor. Then the elevator can go to that floor. — deceze
– deceze ♦, Commented Jan 25, 2015 at 11:23
it s a game : play.elevatorsaga.com/#challenge=3 I don t control the settings :) — Poutrathor
– Poutrathor, Commented Jan 25, 2015 at 11:59

score 1 · Accepted Answer · 2015-06-03 20:16:16Z

First of all, in

floors[0].on("up_button_pressed", function () { 
     elevator.goToFloor(floors[0].floorNum());
});

the floors[0] inside the function is always the same object that the one that is triggering the event, so I would change it to use this:

floors[0].on("up_button_pressed", function () { 
        elevator.goToFloor(this.floorNum());
});

and then, just do it for all floors with forEach:

floors.forEach(function (floor) {
    floor.on("up_button_pressed", function () {
        elevator.goToFloor(this.floorNum());
    });
    // same for "down_button_pressed" here
});

Since handler functions do not need to access outer variable floor and use this, you can even define them out of loop and use them by name, if you wished:

function onFloorUp() {
    elevator.goToFloor(this.floorNum());
}
// same for onFloorUp

floors.forEach(function (floor) {
    floor.on("up_button_pressed", onFloorUp);
    // same for "down_button_pressed" here
});

Amit Joki · Accepted Answer · 2015-01-25 11:23:24Z

1

You can just make use of Array.forEach and refactor your code to the below

floors.forEach(function(floor){
    floor.on('up_button_pressed,down_button_pressed', function(){
       elevator.goToFloor(floor.floorNum());
    });
});

You're not doing anything specific when when up_button_pressed or down_button_pressed is triggered, so just combine those events using a comma.

answered Jan 25, 2015 at 11:23

Amit Joki

59.4k7 gold badges80 silver badges96 bronze badges

Comments

otnieldocs · Accepted Answer · 2015-01-25 11:26:26Z

1

here we go... first you take one of your function that you need to be iterated.

floors[0].on("up_button_pressed", function() { 
        elevator.goToFloor(floors[0].floorNum());
    } );

then you transform that code so that code can work in iteration (for example for loop)

for(var i=0; i<x; i++){
floors[i].on("up_button_pressed", function(i) { 
    elevator.goToFloor(floors[i].floorNum());
}, i ); }

I do that on casperjs, but I think that will be work on regular javascript too...(because casperjs is javascript too)

answered Jan 25, 2015 at 11:26

otnieldocs

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