Looping an array with if and else as well as charAt

I am new to Javascript and I have some experience in C and I cannot figure out what I am doing wrong here. So far Javascript is really confusing and I don't understand it as C is the only programming language I know besides HTML & CSS and I tried these two codes but none of them work.

I am trying to use a for loop and if else statement with charAt. The goal is to look at the first character in an array of names and if the character is a 'j' or 'J' print out "Goodbye" + name and if not print out "Hello" + name. Do I need to convert to ASCII? any insight or recommendations would be great thank you. Here is what I have tried below.

var names = ["Yaakov", "John", "Jen", "Jason", "Paul", "Frank", "Larry", "Paula", "Laura", "Jim"];

for (var i = 0; i < names.length; i++) {
  if (names[i].charAt(0) == 'j' || 'J') {
    console.log("Goodbye " + names[i]);
  } else(names[i].charAt(0) !== 'j' || 'J']) {
  console.log("Hello " + names[i]);
}
}

var names = ["Yaakov", "John", "Jen", "Jason", "Paul", "Frank", "Larry", "Paula", "Laura", "Jim"];

var myFunc = function(letter) {
  for (var i = 0; i < letter.length; i++) {
    if (letter[i].charAt(0) == 'j' || 'J') {
      console.log("Goodbye " + letter[i]);
    }
    if (letter[i].charAt(0) !== 'j' || 'J') {
      console.log("Hello " + letter[i]);
    }
  }
}
myFunc(names);

 if(letter[i].charAt(0)=='j' || 'J'){}

When talking about js it is like C in conditionals: 0 for false and anything for true.
In your code you should put:

if(letter[i].charAt(0)=='j' || letter[i].charAt(0)=='J'){}

Because this is how it is checking if that is the two letters.
The second is:

if(letter[i].charAt(0)!='j' || 'J'){}

The same thing happens. And to solve it I advise you to use the symbol && instead of ||:

if (letter[i].chatAt(0)!='j' && letter[i].charAt(0)!='J'){}

And here I leave you the complete code:

var names = ["Yaakov", "John", "Jen", "Jason", "Paul", "Frank", "Larry", "Paula", "Laura", "Jim"]; 
var myFunc = function (letter) { 
for (var i = 0; i < letter.length; i++) { 
if (letter[i].charAt(0) == 'j' || letter[i].charAt(0)=='J') { 
console.log("Goodbye " + names[i]); 
} 
if (letter[i].charAt(0) != 'j' && letter[i].charAt(0)!='J') {
console.log("Hello " + names[i]); }
 } 
 } 

myFunc(names);

Instead of treating char to char as you would in C I advise you to use this for loop to iterate over the entire array:

for(let i in letter){
if (letter[i].charAt(0)=='J'){}
}

I assure you that in the long run this will save you more time.