variable_global_exists

With this function you can check whether a global scope variable exists or not. You supply the global variable name to check for as a string (see example code below) and the function will return true if a global variable with the given name exists or false otherwise.

Syntax:

variable_global_exists(name);

Returns:

Boolean

Example:

if !variable_global_exists("enemy_num"))
{
global.enemy_num = instance_number(obj_Enemey_Parent);
}

The above code will check to see if the global variable called "enemy_num" exists and if it does not it is created and set a value.