function setting variable when it shouldn't

Question

function genEnemy(a) {
 //javascript:alert(en[0]+'\n'+genEnemy(en[0])+'\n'+en[0])
 with (Math) {
  a[1]=round(a[1]*(.5+random()))
  a[2]=round(a[2]*(1+random()))
  for (var b=0;b<5;b++) a[3][b]=round(a[3][b]*(a[3][b]/2+random()*a[3][b]/10))
  for (var b=0;b<a[4].length;b++) random()<it[a[4][b]][3]/10?a[4][b]=0:0
  }
 return a
 }

Script to generate an enemy's stats given the bases each enemy array. (RPG game) The problem is, when I am expecting it to return an array containing the new stats, it also sets the enemy array to the new one. Why is this? Obviously you can see how problems are caused by this (the bases being changed so a weak enemy can become uber powerful). How would I stop it from setting the array in en (array of enemy values)?

I'm not following what you want it to do, your variable names make it hard to decode your code based o the description. — Nick Craver
– Nick Craver, Commented Nov 15, 2010 at 0:11

casablanca · Accepted Answer · 2010-11-15 00:11:48Z

6

Objects are passed by reference in JavaScript. That means any changes you make to the array a inside genEnemy is reflected on the original array that was passed in. You need to make a deep copy of the array and return this copy. Here is a function that will do it for you:

function cloneArray(a) {
  var b = [];
  for (var i = 0; i < a.length; i++)
    if (a[i] instanceof Array)
      b[i] = cloneArray(a[i]);
    else
      b[i] = a[i];
  return b;
}

Inside genEnemy, you would then do:

a = cloneArray(a);
// make changes to the new array
return a;

Also, don't forget to include semicolons in your code. Even though they are optional, you may run into unexpected problems if you get into the habit of omitting them.

answered Nov 15, 2010 at 0:11

casablanca

70.9k8 gold badges139 silver badges155 bronze badges

Sign up to request clarification or add additional context in comments.

8 Comments

Anonymous Over a year ago

Is there a way to do this without another function? I just hate adding functions for little things.

alex Over a year ago

@Ruffian Take out the function body and run it procedurally and you don't have a function :P But remember turning often used and useful code into a function is a good thing.

casablanca Over a year ago

@Ruffian: If there was a built-in function, I would have definitely suggested that. Unfortunately there isn't.

Anonymous Over a year ago

Meh. I'll just take out the genEnemy function and find a way to put it into a larger function to set up the whole fight. Thanks anyway.

alternative Over a year ago

@Ruffian be careful with that thinking - Abstraction into separate functions is a good thing!

|

MSI · Accepted Answer · 2010-11-15 00:13:34Z

0

Are you passing array en to your getEnemy() function? If so then it will change the values in en array as it's passed by reference not by value

answered Nov 15, 2010 at 0:13

MSI

1,1348 silver badges23 bronze badges

Collectives™ on Stack Overflow

function setting variable when it shouldn't

2 Answers 2

8 Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

8 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related