How to see if an array has a value, and return true if it does. - JavaScript [duplicate]

In your code where you are returning false, you are returning too soon (before checking all elements)

you should return false after the loop is finished

function containsHello(array){
  for(let i = 0; i < array.length; i++){
    if(array[i] === 'hello'){
      return true;
    }
  }
  return false;
}

Basically, if the element is NOT 'hello', it immediately returns false but hasn't got a chance to check any potentially preceding elements. Remember if a function reaches a return statement it (prematurely) ends. Just a small logic mistake.

Also...

includes is a method. I don't even need to explain.

var someList = ['a', 'b', 'c'];
console.log(someList.includes('c')) // --> true

Thats because for the second the hello is at index position 1. While iterating over the array, it sees the 'no' value first and just returns.

The problem with your code is that it will always return on the first item, and never check the other values. Remove the else block, and return false after the loop.

Alternatively, just use array.includes().

You are returning false if the first element is not equal to 'hello'
Instead try this function

function containsHello(array){
  for(let i = 0; i < array.length; i++){
    if(array[i] === 'hello'){
      return true;
    }
  }
  return false
}

There is a logical error in your function. It returns false if the first element is not 'hello'. However, this does not make sense, as 'hello' could still be contained in the other values. This can be fixed by returning false only after checking all of the values.

function containsHello(array){
  for(let i = 0; i < array.length; i++){
    if(array[i] === 'hello'){
      return true;
    }
  }
  return false;
}

console.log(containsHello(['hello', 'no', 'yes']));
console.log(containsHello(['no', 'hello', 'yes']));
console.log(containsHello(['no','yes','also no']));

It could be better this:

function containsHello(array){
  return array.indexOf('hello') !== -1; 
}

You could use .includes() if you want to skip the for loop.

function containsHello(array){
  if(array.includes("Hello")) {
     return true;
  } else {
    return false;
  }
}

or you could do the following if you want to search for different words

function containsWord(word, array){
      if(array.includes(word)) {
         return true;
      } else {
        return false;
      }
    }

You can use the .includes() function for this purpose like this:

[].includes('value')

Then:

console.log(['no','hello','yes'].includes('hello')); //logs true
console.log(['hello','no','yes'].includes('hello')); //logs true