When to use functions?

Is using custom functions a preference? It's possible to make a game work with everything happening inside event listeners but I want to know how often should I use functions. Like in a game of Tic Tac Toe, if I click on a square it will change color, the turn variable will change, check if there are any winners or anymore moves. For all that I just put all the results in that Mouse_CLICK event listener. I don't know when I should use custom functions.

use custom function when you are repeating a lot of code. If you notice you are maybe drawing a line, or attaching several textboxes, create a function that means you only have to enter a line of code every time you want to draw that line or attach that textbox.

For instance

PHP Code:

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function createTextField(varName:TextField,varWidth:Number,xPos:Number,yPos:Number,wWrap:Boolean){
            varName.width=varWidth;
            varName.x = xPos;
            varName.y = yPos;
            varName.wordWrap=wWrap;
            trace(varName)
            addChild(varName); 


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then each time you want to attach a textbox its a case of

PHP Code:

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createTextField(output5_txt,170,330,269,true); 


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which makes it look tidy and it's less typing for you

It's worth noting that eventHandlers are functions. Essentially you'd want to use a function for any code that is deferred (eg. not run when you hit a frame on a timeline or when your document class is initialized) or any code that you want to run more than once.