For (k=0; k fontN.length; k++){

Question

There are 6 buttons and If this code is the only code in the fla why isn't the trace showing results? How can I make trace (fontN[k]) show which button I clicked??
var fontN:Array = [Tx_btn1, Tx_btn2, Tx_btn3, Tx_btn4, Tx_btn5, Tx_btn6]; //buttons
var fontF:Array = [format1, format2, format3, format4, format5, format6];
for (k=0; k<fontN.length; k++){
    fontN[k].ivar=k;
fontN[k].onRelease = function() {
trace (fontN[k]) // it allways shows '_level0.Tx_btn6'
my_txt.setNewTextFormat(fontF[this.ivar]);
trace (fontF[this.ivar]) // 'undefined'

Answer 1

(i changed ivar to kvar.  it's just a variable name but i like to use something suggestive:  namely the kvar and k variable are related.  because i use i in most of my for-loops, most of my code uses ivar.)
anyway:
var fontN:Array = [Tx_btn1, Tx_btn2, Tx_btn3, Tx_btn4, Tx_btn5, Tx_btn6]; //buttons
var fontF:Array = [format1, format2, format3, format4, format5, format6];
for (k=0; k<fontN.length; k++){
    fontN[k].kvar=k;  // if you're using simple buttons, this won't work.  use movieclip buttons.
fontN[k].onRelease = function() {
trace (fontN[this.kvar]) // k will be the last value in your for-loop because you're clicking after the for-loop completes
my_txt.setNewTextFormat(fontF[this.kvar]);
trace (fontF[this.kvar]) // 'undefined' if format1, etc undefined