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

For those looking for an ES6 alternative using arrow functions, you can do the following.

let startsWith = wordToCompare => (element, index, array) => {
  return element.indexOf(wordToCompare) === 0;
}

// where word would be your argument
let result = addressBook.filter(startsWith("word"));

Updated version using includes:

const startsWith = wordToCompare => (element, index, array) => {
  return element.includes(wordToCompare);
}