What is the fastest way to scan a JS array

Question

I am making a local login using JavaScript and I need to know the fastest way to scan an array.

Say there are two arrays:

usernames = ["uname 1", "uname 2", "uname 3"];
passwords = ["pswd 1", "pswd 2", "pswd 3"];

And there are two HTML inputs

<input id="username">
<input id="password">

I need to know the fastest way to see if the value from the HTML inputs matches any username and password.

I have tried a while function:

while(counter1 < usernames.length){
   //testing goes here
   counter ++;
}

And an "if / repeate" function

if(counter1 < usernames.length){
    //testing goes here
    setTimeout(currentFunction, 1);
}

This is not a duplicate of the question "What's the fastest way to loop through an array in JavaScript?" because I am open to more than a

for

loop

Answer 1

For "the fastest" to matter, I assume there must be a lot of entries in the array — like, millions. If so, I'd definitely offload to native code by using Array#indexOf or Array#includes (if all you need to know is whether there's a match). Otherwise, really, it doesn't matter.