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JavaScript JavaScript Loops, Arrays and Objects Tracking Multiple Items with Arrays Iterating through an Array

Posted by Cristian Castro
Cristian Castro
Courses Plus Student 12,666 Points

What is the difference between [] and () in this code challenge?

I was solving this code challenge and I came across this... var temperatures = [100,90,99,80,70,65,30,10]; for ( var i = 0; i < temperatures.length; i += 1) { console.log(temperatures(i)) } It said it was wrong. Then I did this... var temperatures = [100,90,99,80,70,65,30,10]; for ( var i = 0; i < temperatures.length; i += 1) { console.log(temperatures[i]) } and it was right.

My question is... What happens if I use ()?

script.js 
var temperatures = [100,90,99,80,70,65,30,10];
for ( var i = 0; i < temperatures.length; i += 1) {
  console.log(temperatures[i])
}
index.html 
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JavaScript Loops</title>
</head>
<body>
<script src="script.js"></script>
</body>
</html>

3 Answers

Joey Ward
PLUS
Joey Ward
Courses Plus Student 24,778 Points
Joey Ward
Joey Ward
Courses Plus Student 24,778 Points

When you use "temperatures(i)", the browser thinks you are passing the value of a variable "i" as an argument to a function "temperatures".

If "temperatures" is an array (not a function) the. The browser won't know what to do when your code is written as if it's trying to pass an argument to a function.

To call an index from an array, you would use [] rather than ().

Since your code is looping over an array and calling the value at each index, you want to use "temperatures[i]".

Kevin Delva
Kevin Delva
1,543 Points
Kevin Delva
Kevin Delva
1,543 Points

From what I understand 'temperature' is the array, and to access any item in an array you would use it like this: temperature[x], x being the index in which the item in the array is. So in this case: console.log(temperature[i]); i is the variable that is representing the index in which the item of the array is (and it will be changing according to your for loop), so just as you would access an item in an array like this temperature[x], you can't use "( )" in the code, as only brackets "[ ]" can be used for it. I'm still quite new, sorry if I couldn't explain it better for you. Hope I could help! :)

jason chan
jason chan
31,009 Points
jason chan
jason chan
31,009 Points 
var temperatures = [100,90,99,80,70,65,30,10];
temperatures = temperatures.reverse();
for ( var i = 0; i < temperatures.length; i += 1) {
  console.log(temperatures[i])
}

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reverse

That's how i did it. I used reverse.