I have an array of strings that I am wanting to filter.

var words = ['hello', 'sunshine', 'apple', 'orange', 'pineapple'];

I am wanting to keep only the words that include the letter ‘a’.

var wordsWithA = words.filter(function (word) {
  return words.indexOf('a', 4);
  
});

how do you accomplish this using indexOf in javascript?

>Solution :

indexOf returns -1, if it doesn’t find the element in the container. You should use indexOf on each string word and not on the array words:

var words = ['hello', 'sunshine', 'apple', 'orange', 'pineapple'];

var wordsWithA = words.filter(function (word) {
  return word.indexOf('a') !== -1;
});

console.log(wordsWithA);