I find myself a little mixed up with this syntax in JavaScript: `arr.indexOf(searchElement[, fromIndex])`

Question

I find myself a little mixed up with this syntax in JavaScript: `arr.indexOf(searchElement[, fromIndex])`

   const beasts = ['ant', 'bison', 'camel', 'duck', 'bison'];

console.log(beasts.indexOf('bison'));
// expected output: 1

// start from index 2
console.log(beasts.indexOf('bison', 2));
// expected output: 4

console.log(beasts.indexOf('giraffe'));
// expected output: -1

I've been diving into this JavaScript syntax. I stumbled upon this code snippet on https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/indexOf and it talks about the fromIndex parameter being the starting point for the search. However, as I analyze the following lines of code:

// start from index 2
console.log(beasts.indexOf('bison', 2));
// expected output: 4

I noticed that Camel is at index 2. But how does the counting lead to an expected output of 4?

Just experimenting by changing the second parameter:

// start from index 3
console.log(beasts.indexOf('bison', 3));

With Duck appearing at index 3, I still get an output of 4 for indexOf('bison', 3).

How exactly does this counting work?

javascript arrays indexof

Answer 1

Answer №1

This function simply indicates the specific index where the element is located, without performing any counting.

For instance, if you enter

console.log(beasts.indexOf('bison', 3));

, your search will commence from index 3. Despite this, the result will still be 4 because 'bison' can be found at index 4. The very name indexOf implies that it reveals the index of the specified element.

The array remains unchanged; only the starting position for the search shifts to index 3.

const beasts = ['ant', 'bison', 'camel', 'duck', 'bison'];
                                            ^
                                            |
                                            |
                    Commence searching from this point to the right for "bison"

Answer 2

This function simply indicates the specific index where the element is located, without performing any counting.

For instance, if you enter

console.log(beasts.indexOf('bison', 3));

, your search will commence from index 3. Despite this, the result will still be 4 because 'bison' can be found at index 4. The very name indexOf implies that it reveals the index of the specified element.

The array remains unchanged; only the starting position for the search shifts to index 3.

const beasts = ['ant', 'bison', 'camel', 'duck', 'bison'];
                                            ^
                                            |
                                            |
                    Commence searching from this point to the right for "bison"

Answer 3

Answer №2

Extremely straightforward.

The initial element has an index of 0:

> console.log(creatures[0])
"bear"

If you provide a second parameter to indexOf, it will iterate through your array.
Meaning, if the element is not found starting from the index you specify and moving forward, the search will continue from the beginning, continuing the sequence.

Answer 4

Extremely straightforward.

The initial element has an index of 0:

> console.log(creatures[0])
"bear"

If you provide a second parameter to indexOf, it will iterate through your array.
Meaning, if the element is not found starting from the index you specify and moving forward, the search will continue from the beginning, continuing the sequence.

Answer 5

Answer №3

The focus here is not on counting, but rather on the position of an element within a zero-index array.

You may be feeling unsure because the word bison has two different indexes in this case. However, remember that this word appears twice in the array. Even without using the indexOf method, it is clear that the word is located at both index 1 and index 4.

Answer 6

The focus here is not on counting, but rather on the position of an element within a zero-index array.

You may be feeling unsure because the word bison has two different indexes in this case. However, remember that this word appears twice in the array. Even without using the indexOf method, it is clear that the word is located at both index 1 and index 4.

I find myself a little mixed up with this syntax in JavaScript: `arr.indexOf(searchElement[, fromIndex])`

Answer №1

Answer №2

Answer №3

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