如何进行不区分大小写的文本输入？

Question

My friend is working on a fun Javascript web application where you type something in the text box, and the computer returns you a result, but it is case-sensitive. Can he make it case-insensitive? We have tried to use:

var areEqual = string1.toUpperCase() === string2.toUpperCase();

which was on JavaScript case insensitive string comparison , but he cannot figure out how to use that.

function isValid() {
    var password = document.getElementById('password').value;

    if (password == "Shut Up")
        { alert('HOW ABOUT YOU!') }

    else if (password == "No")
        { alert('You just did') }

}

Answer 1

Just add the .toUpperCase() behind your variables:

else if (password == "No")
  {alert('You just did')}

becomes:

else if (password.toUpperCase() == "No".toUpperCase())
  {alert('You just did')}

or just:

else if (password.toUpperCase() == "NO") //Notice that "NO" is upper case.
  {alert('You just did')}

Answer 2

You can use that this way, for example in the first else-if block:

 else if (password.toUpperCase() == "No".toUpperCase())
 {alert('You just did')}

The function toUpperCase, applied to a string, returns it's uppercased version, so for No it would be NO. If the password variable holds any lower-upper case combo of the word no, such as "No", "nO", "NO" or "no", then password.toUpperCase() will be "NO". The previous code is equivalent to

 else if (password.toUpperCase() == "NO")
 {alert('You just did')}

Answer 3

Please, if you're going to do this, use switch ! The only real difference between toLowerCase as opposed to toUpperCase here is that the values in the case lines won't be shouting at you.

function isValid() {
    var password = document.getElementById('password').value;

    switch (password.toLowerCase()){
        case "shut up":
            alert('HOW ABOUT YOU!');
        break;
        case "no":
            alert('You just did');
        break;
        case "okay":
            alert('Okay');
        break;

        // ...

        case "something else":
            alert('Really?');
        break;
        default:
            alert('Type Something Else')
    }
}