Compare variable against element of an array (java script)

Question

I am trying to compare each element of an array with the user input to generate a message if the user's input doesn't match with any element of the array. The code I use to do is below.

var guess_input;
var finished = false;
var colors = ["Aqua", "BurlyWood", "Cornsilk", "DarkGrey", "DarkRed", "Indigo", "LightGrey"];

while (!finished) {
          guess_input = prompt("I'm thinking of one of these colors:\n\n" + "Aqua, BurlyWood, Cornsilk, DarkGrey, DarkRed, Indigo, LightGrey" + "\n\nWhat is the color I'm thinking of?");
          finished = check_guess();
          }
      }
      function check_guess() {

       if (guess_input !=  colors[0] || guess_input != colors[1] || guess_input != colors[2] || guess_input != colors[3])  {
          alert("Sorry, I don't recognize that color!\n\n" + "Please try again.");
          return false;
        }
}

the problem with this code is that if I only select one element from array, it works perfectly fine. but when I use 'OR' operator, it doesn't work. Is there any better way to do this? I am new with java script.

Thanks!

Why are you declaring the function inside your loop? Declare it outside, so you don't iterate over function creation everytime — Sterling Archer
– Sterling Archer, Commented Sep 4, 2016 at 19:28
@Jonasw, this would only work, if all elemebt are to check, but not only a part of it, like element 0 ... 2. — Nina Scholz
– Nina Scholz, Commented Sep 4, 2016 at 19:50

Nina Scholz · Accepted Answer · 2017-04-03 13:00:04Z

You could use the logical AND operator &&, because you need a check for all colors to be checked.

if (guess_input != colors[0] && guess_input != colors[1] && guess_input != colors[2] && guess_input != colors[3])  {
     alert("Sorry, I don't recognize that color!\n\n" + "Please try again.");
    return false;
}

For a working code, you need to return true for a found color, as well.

var guess_input;
var finished = false;
var colors = ["Aqua", "BurlyWood", "Cornsilk", "DarkGrey", "DarkRed", "Indigo", "LightGrey"];

while (!finished) {
    guess_input = prompt("I'm thinking of one of these colors:\n\n" + "Aqua, BurlyWood, Cornsilk, DarkGrey, DarkRed, Indigo, LightGrey" + "\n\nWhat is the color I'm thinking of?");
    finished = check_guess();
}

function check_guess() {
    if (guess_input != colors[0] && guess_input != colors[1] && guess_input != colors[2] && guess_input != colors[3]) {
        alert("Sorry, I don't recognize that color!\n\n" + "Please try again.");
        return false;
    }
    return true; // necessary, otherwise the function returns undefined, which is a falsy value
}

Brian Peacock · Accepted Answer · 2016-09-04 19:57:25Z

0

You need to compare guess_input against the items in the colours array. This is a perfect job for the Array.prototype.some() method, which returns true or false depending on a condition defined in its callback. For example...

var test_guess = colours.some(function(color) {
    /* 'color' = each item in 'colours' */
    return color === guess_input;
});

if (test_guess) {
   /* correct .....  */
} else {
   /* incorrect .... */
}

Here .some() begins to iterate through all the items in the colours array until the condition returns true. The variable test_guess will be true if the guess matches a colour, otherwise false.

See: Array.prototype.some() @ MDN

answered Sep 4, 2016 at 19:57

Brian Peacock

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