JavaScript check if letter is contain or not in a string

Question

I have the following JavaScript function using which I want to check if the first element of the array called mutation contains all the letters of the second element.

function mutation(arr) {
  let test    = arr[1].toLowerCase();
  let target  = arr[0].toLowerCase();

  let split = test.split('');

  split.forEach((elem)=>{
    if(target.indexOf(elem) < 0 ) {
      return false;
    }
  });
  return true;
}

mutation(["hello", "hey"]);

Now it should show me boolean false because letter y does not exist in hello word. but it's doesn't.

Is there anything I am doing wrong?

You cannot `return` from inside `forEach`. Please refer https://stackoverflow.com/questions/34653612/what-does-return-keyword-mean-inside-foreach-function — Abhishek, Aug 04 '20 at 05:28

Umair Khan · Answer 1 · 2020-08-04T05:46:18.800

3

You may use Array.prototype.every()

function mutation(arr) {
  let test = arr[1].toLowerCase();
  let target = arr[0].toLowerCase();
  let split = test.split('');
  return split.every(x => target.includes(x)); // checks if all letters of `split` exists in `target`
}
console.log(mutation(["hello", "hey"]));
console.log(mutation(["hello", "heo"]));
console.log(mutation(["helloworld", "lloword"]));

edited Aug 04 '20 at 05:46

answered Aug 04 '20 at 05:36

Umair Khan

1,684
18
34

Abhishek · Accepted Answer · 2020-09-07T04:11:15.133

1

You can try another approach to get the expected results:

function mutation(arr) {
  let test    = arr[1].toLowerCase().split('').join('');
  let target  = arr[0].toLowerCase().split('').join('');
  return target.includes(test);
}

mutation(["hello", "hey"]);

edited Sep 07 '20 at 04:11

answered Aug 04 '20 at 05:36

Abhishek

539
5
25

3

I don't think this would work. Try with `['hello world', 'hello']`. The sorted strings are `[" dehllloorw", "ehllo"]`, where `includes` returns `false` – Maxime Helen Aug 04 '20 at 05:45

Maxime Helen · Answer 3 · 2020-08-24T22:33:10.350

1

I would do:

function mutation(arr) {
  let test    = arr[1].toLowerCase();
  let target  = arr[0].toLowerCase();
  return target.includes(test);
}

console.log(mutation(["hello", "hey"]));
console.log(mutation(["helloworld", "hello"]));

edited Aug 24 '20 at 22:33

answered Aug 04 '20 at 05:41

Maxime Helen

1,382
7
16

Alok Takshak · Answer 4 · 2020-08-04T05:51:19.653

The Return statement inside the ForEach won't return from the function, you can use a simple for loop or a reduce to get the end result in on line

function mutation(arr) {
  let test    = arr[1].toLowerCase();
  let target  = arr[0].toLowerCase();

  let split = test.split('');

  const result = split.reduce((acc, curr) => acc && target.includes(curr), true);

  return result;
}

console.log(mutation(['hello', 'y']));

score 0 · Answer 5 · answered Aug 04 '20 at 05:36

Stick to more classical methods:

console.log(mutation(["hello", "hey"]));

function mutation(args) {
  const target  = args[0].toLowerCase();
  const test    = args[1].toLowerCase();
  
  for(let i = 0; i < test.length; i += 1) {
  
    if (target.indexOf(test[i]) < 0) {
      return false;
    }
    
  }
  return true;
}

JavaScript check if letter is contain or not in a string

5 Answers5