JAVASCRIPT

javascript not null

if (variable !== null) {
  console.log("Var is NOT null");
}

javascript check if null

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
}

js if not undefined or null

if(variable == null) //variable is undefined or null