//Even if the value is 0, this will execute. if (myVar !== null) {...}
//If you don't want it to execute when it's 0, then set it asif (myVar) {...}
//This will return false if var value is 0.
if (variable === null) { //Executes only if variable is null but not undefined//Code here
}
if (variable == null) { //Executes if variable is null OR undefined//Code here
}