Question

I am making an javascript game, featuring several levels, stored in json.
When loading, I run a function to “parse” the level object by replacing values that are not present by their default values, or by replacing some values by objects, such as:

//i is the variable I use to loop through the enemies

if (typeof(level.enemies[i].life)=="undefined") {
 level.enemies[i].life=100;
}

if (typeof(level.enemies[i].follow)=="number") {
 level.enemies[i].follow=level.enemies[level.enemies[i].follow];
 // replace the number of the enemy,
 // by a reference to the actual enemy.
}

The problem is that I have a lot of “ifs” similar to these throughout the function, and I am wondering if I somehow can reduce them to a function so I can do this:

replaceByType(level.enemies[i].life,"undefined",100);
replaceByType(level.enemies[i].follow,"number",level.enemies[level.enemies[i].follow]);

Sadly I don’t know how to do this, because their is no way to pass a variable(other than an object) by reference. Maybe there is another way to simplify my code?

Answer 1

Since you can pass objects by reference, you can pass a property of the object that you want to replace.

function replaceByType(obj, property, type, value) {
   if(typeof obj[property] === type) {
     obj[property] = value;
   }
}

Which you can call almost how you were wanting to:

replaceByType(level.enemies[i], "life", "undefined", 100); 
replaceByType(level.enemies[i], "follow", "number", level.enemies[level.enemies[i].follow]);