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Q&A Function.prototype.call()

I wanted to print to browser console the number of li list items of a given ul list. This didn't work (console output was undefined): console.log(document.querySelectorAll(".example").length); ...

1 answer · posted 3y ago by deleted user · edited 3y ago by Alexei‭

Question javascript function prototype

#3: Post edited by

Alexei‭ · 2021-08-27T06:46:19Z (about 3 years ago)
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javascript function prototype

#2: Post edited by (deleted user) · 2021-08-19T16:34:36Z (over 3 years ago)

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I wanted to print to browser console the number of `li` list items of a given `ul` list.
~~This didn't work (output was _undefined_):~~
```js
console.log(document.querySelectorAll(".example").length);
```
~~This worked (output was a plausible number):~~
```js
[].filter.call(
document.getElementsByClassName('example')[0].children,
function (el) {
return el.nodeName === 'LI';
}
).length
```
## My question
It was written in the [MDN page for Function.prototype.call()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call):
> The call() method calls a function with a given this value and arguments provided individually.
But in the working code there was no "this".
What is the meaning of "call" in the second code?

I wanted to print to browser console the number of `li` list items of a given `ul` list.
This didn't work (console output was _undefined_):
```js
console.log(document.querySelectorAll(".example").length);
```
This worked (console output was a plausible number):
```js
[].filter.call(
document.getElementsByClassName('example')[0].children,
function (el) {
return el.nodeName === 'LI';
}
).length
```
## My question
It was written in the [MDN page for Function.prototype.call()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call):
> The call() method calls a function with a given this value and arguments provided individually.
But in the working code there was no "this".
What is the meaning of "call" in the second code?

#1: Initial revision by (deleted user) · 2021-08-19T16:27:23Z (over 3 years ago)

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Function.prototype.call()

I wanted to print to browser console the number of `li` list items of a given `ul` list.

This didn't work (output was _undefined_):

```js
console.log(document.querySelectorAll(".example").length);
```

This worked (output was a plausible number):

```js
[].filter.call(
    document.getElementsByClassName('example')[0].children, 
    function (el) {
        return el.nodeName === 'LI';
    }
).length
```

## My question

It was written in the [MDN page for Function.prototype.call()](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/call):

 > The call() method calls a function with a given this value and arguments provided individually.

But in the working code there was no "this".

What is the meaning of "call" in the second code?

javascript

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