CODEWITHSUNDEEP
javascriptarraysparenthesesbrackets
user276800
user276800

Reputation: 11

Javascript: why do functions treat array() and array[] differently?

In class, teacher couldn't explain why tweets(i) failed and tweets[i] works:

  var tweets=["hi","who","when","where","bye"];
  alert("start");
  for (var i=0; i < tweets.length; i++) {

    alert(tweets[i]);
  }
  alert("finish");

Upvotes: 1

Views: 90

Answers (3)

Tr1et
Tr1et

Reputation: 895

The () is a method invocation operator and the [x] is an member access operator. As array is not a function (e.g. typeof array !== 'function'), so you can only use member access operator on the array.

Note:

  • I don't know the specification name of the above operators, will need expert explanation on them.
  • A function is an object so you can use both operators on it

e.g.

var func = function() { return 'hello'; };

func.world = 'earth'
console.log(func());
console.log(func['world'])
console.log(func.world)

Upvotes: 0

Simon Hyll
Simon Hyll

Reputation: 3618

Brackets are used for functions, so array() would be a function called array. Square brackets are used for arrays, so array[] would be an array. array[0] is the first entry in an array, array(1) would send 1 as an argument to a function called array.

And stop going to classes where the teacher can't explain something this simple. They clearly aren't a programmer.

Upvotes: 2

Jonathan
Jonathan

Reputation: 104

The reason tweets(i) fails in this code snippet is because, when you say tweets(i), javascript looks at it and says "oh, the code wants me to go find a function named tweets and execute it with a parameter named i."

When javascript sees tweets[i], it says "oh, this isn't a function. The code wants me to find the number-i place in an array and give it back the value stored there.

In short, The reason tweets(i) doesn't work is because you're telling it to alert a function that you haven't defined.

Upvotes: 1

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