Check if a string contains any element of an array in JavaScript

Problem lies in the for loop, which only iterates once since return ends the function, cutting off the for loop in the process. So, you can update the code like so to make the function only return once the for loop has been completed .

var arr = ['banana', 'monkey banana', 'apple', 'kiwi', 'orange'];

function checker(value) {
  var prohibited = ['banana', 'apple'];

  for (var i = 0; i < prohibited.length; i++) {
    if (value.indexOf(prohibited[i]) > -1) {
      return false;
    }
  }
  return true;
}

arr = arr.filter(checker);
console.log(arr);

For reducing the function you can use every() and indexOf() methods

The 'every' method executes the provided callback function once for each element present in the array until it finds one where callback returns a falsy value (a value that becomes false when converted to a Boolean). If such an element is found, the every method immediately returns false. Otherwise, if callback returned a true value for all elements, every will return true. callback is invoked only for indexes of the array which have assigned values; it is not invoked for indexes which have been deleted or which have never been assigned values.(Taken from here)

var arr = ['banana', 'monkey banana', 'apple', 'kiwi', 'orange'];

function checker(value) {
  var prohibited = ['banana', 'apple'];
  return prohibited.every(function(v) {
    return value.indexOf(v) == -1;
  });
}

arr = arr.filter(checker);
console.log(arr);

For older browser check polyfill option of every method.

You could even use a regex here. Generate regex using the array and use test() to check match

var arr = ['banana', 'monkey banana', 'apple', 'kiwi', 'orange'];

function checker(value) {
  var prohibited = ['banana', 'apple'];
  var regex = new RegExp(prohibited.map(function(s) {
    return s.replace(/[-/\\^$*+?.()|[\]{}]/g, '\\$&')
  }).join('|'));
  return !regex.test(value);
}

arr = arr.filter(checker);
console.log(arr);

Refer this answer for string to regex conversion : Can you create JavaScript regexes on the fly using string variables?

You can use some() function: to check if a string contains any element of an array.

e.g.

var fruitsArr = ['banana', 'monkey banana', 'apple', 'kiwi', 'orange'];
var myString = "I have an apple and a watermelon.";
var stringIncludesFruit = fruitsArr.some(fruit => myString.includes(fruit));

This function is pretty new. some() method accepts a callback where you define the condition you want to verify and it returns a boolean. Check the documentation at the link above.

It can be as simple as that:

const arr = ['banana', 'monkey banana', 'apple', 'kiwi', 'orange'];

const checker = value =>
  !['banana', 'apple'].some(element => value.includes(element));

console.log(arr.filter(checker));

ECMAScript 6 FTW!

The checker uses an arrow function.

The ! means that it will exclude all elements that doesn't meet the conditions.

The some() method tests whether some element in the array passes the test implemented by the provided function.

_{from Array.prototype.some() docs on MDM}

The includes() method determines whether one string may be found within another string, returning true or false as appropriate.

_{from String.prototype.includes() docs on MDM}

As some latest ECMAScript features aren't supported in all browsers, you should use Babel to compile your code to ECMAScript 5.