How do I pass an extra parameter to the callback function in Javascript .filter() method?

Question

I want to compare each string in an Array with a given string. My current implementation is:

function startsWith(element) {
    return element.indexOf(wordTo         


        

Answer 1

The second parameter of filter will set this inside of the callback.

arr.filter(callback[, thisArg])

So you could do something like:

function startsWith(element) {
    return element.indexOf(this) === 0;
}
addressBook.filter(startsWith, wordToCompare);