Question

I’m trying to update a variable that exists outside of a loop from within the loop like this:

var firstRun = true;
console.log("firstRun is " + firstRun);
if(firstRun == true){
    console.log("This is your first run");
    firstRun = false;
}else{
    console.log("You have already run this loop at least once");
};

Assuming this code block is within a larger one that would run 4 times I would expect it to output This is your first run once, then You have already run this loop at least once three times. Instead I get This is your first run 4 times and the console.log("firstRun is " + firstRun); always outputs true

I’m sure this is an issue with scope that I don’t quite understand. Forgive me, I come from the land of Ruby 🙂

Answer 1

You are redeclaring firstRun every step in the loop. Move var firstRun = true; out of the loop.

If you can’t move it out of the loop, you’ll have to use an object, and check if it’s been declared before assigning the object:

var firstRun = firstRun || {ran: false};

if (firstRun.ran == true) {
    console.log("This is your first run");
    firstRun.ran = false;
} else {
    console.log("You have already run this loop at least once");
};