如何提示直到条件满足？

Question

Im trying to prompt the user until the input is equal to one of the elements in the array?

do {
      var bestCities = ["miami","sanfrancisco","austin","chicago","phoenix"]
      var userInput = prompt('Whats your city?');
    } while (
        userInput !== bestCities[i]
      );
    alert('I love ' + i + ' also' );

Answer 1

Could be:

 var bestCities = ["miami","sanfrancisco","austin","chicago","phoenix"]; var userInput; do{ userInput = prompt('Whats your city?') } while (bestCities.indexOf(userInput) === -1); alert('I love ' + userInput + ' also' ) 

indexOf() returns the position from an array.

indexOf returns -1 when no matches were found. So the loop ends when it finds an index other than -1 . For example miami is in the 0 position and chicago in the 3 position.

Answer 2

Here's a better architecture:

var validCity = false;

while(!validCity) {
    var input = prompt("What is your city");
    if(bestCities.indexOf(input) != -1) validCity = true;
}

Answer 3

do {
      var bestCities = ["miami","sanfrancisco","austin","chicago","phoenix"]
      var userInput = prompt('Whats your city?');
    } 
while (bestCities.indexOf(userInput)==-1);
alert('I love ' + userInput  + ' also' );

Just a check in array index will do the trick

Answer 4

An even better way to do it:

const bestCities = ["miami", "sanfrancisco", "austin", "chicago", "phoenix"];
let userInput;
do {
  userInput = prompt("Whats your city?");
} while (!bestCities.includes(userInput));
alert(`I love ${userInput} also`);

Note: This is just an improvement to the current most top answer.