this.filter is not a function

Asked Apr 08 '20 at 17:51

Active Apr 08 '20 at 17:57

Viewed 24 times

I get an error with the following code:

Array.prototype.remove = function(value) {
    return this.filter((element) => element != value); //TypeError: this.filter is not a function
}

([2, 3, 8, 9]).remove(3);

Can someone explain why? I do not get the same results when using a String function:

String.prototype.toTitleCase = function() {
    return this.replace(/\b\w+/g,
        (txt) => (txt.charAt(0).toUpperCase() + txt.substr(1).toLowerCase())
    ); // Works perfectly with no errors
}

I am using the latest version of Firefox (75.0, 64-bit)

edited Apr 08 '20 at 17:57

asked Apr 08 '20 at 17:51

grahamcracker1234

What browser version? – Taplar Apr 08 '20 at 17:54
I copied and pasted your code into a node.js 12.16 REPL and it worked as expected. what runtime are you using? – Dan O Apr 08 '20 at 17:55
@Taplar I am using the latest version of Firefox – grahamcracker1234 Apr 08 '20 at 17:55
@DanO I am using the latest version of Firefox – grahamcracker1234 Apr 08 '20 at 17:56
In jsfiddle for some reason the `this` is the `Window` object. – Taplar Apr 08 '20 at 17:57
1

Works fine if you use an explicit `new Array()` and push to it before doing the remove call though – Taplar Apr 08 '20 at 17:59
Changing it from Array.prototype.remove to Object.prototype.remove causes the `([])` form to work, which suggests that the `([])` version is not considered an instantiation of the Array class. – Taplar Apr 08 '20 at 18:01
4

It's a missing semicolon. – Bergi Apr 08 '20 at 18:04
Woah, nice catch on the duplicate. I wouldn't have ever thought about that. – Taplar Apr 08 '20 at 18:05
@Bergi of course its a semicolon, thank you! – grahamcracker1234 Apr 08 '20 at 18:38

this.filter is not a function

0 Answers0