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");
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Because that is the convention as every programming language uses brackets to access an assay?user3773246– user37732462018-01-01 05:58:54 +00:00Commented Jan 1, 2018 at 5:58
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1You wouldn't be able to use tweets() because that means you are calling the tweets function, which doesn't exist. "tweets" is not a function it is an array.Joshua Schaeffer– Joshua Schaeffer2018-01-01 06:00:53 +00:00Commented Jan 1, 2018 at 6:00
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Because tweets isn't a function, its an array and you access elements in an array using square brackets only.vibhor1997a– vibhor1997a2018-01-01 06:00:55 +00:00Commented Jan 1, 2018 at 6:00
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2Round brackets after an expression are always for function calls, and square brackets after an expression are always for property access. Array values are properties.Ry-– Ry- ♦2018-01-01 06:01:32 +00:00Commented Jan 1, 2018 at 6:01
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3 Answers
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.
Comments
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.
Comments
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)
