javascript - Switch Statement, it does not work with prompt - Stack Overflow

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I just learned switch statements. I was practicing it by building something. When i set the value of variable to a number it works but when i asks the user for a number it always outputs the default statement.

It works with this code:

confirm("You want to learn basic counting?");
var i = 0;
switch (i) {
    case 0:
        console.log(i);
        i++
    case 1:
        console.log(i);
        i++;
    case 2:
        console.log(i);
        i++;
    case 3:
        console.log(i);
        i++;
    case 4:
        console.log(i);
        i++;
    case 5:
        console.log(i);
        i++;
    case 6:
        console.log(i);
        i++;
    case 7:
        console.log(i);
        i++;
    case 8:
        console.log(i);
        i++;
    case 9:
        console.log(i);
        i++;
    case 10:
        console.log(i);
        console.log("Congratulations!");
        break;
    default:
        console.log("Buzz, wronghh");
        break;
}

But when i asks value from user, it dosen't work. Code below doesn't work:

confirm("You want to learn basic counting?");
var i = prompt("Type any number from where you want to start counting[Between 0 and 10]");
switch (i) {
    case 0:
        console.log(i);
        i++
    case 1:
        console.log(i);
        i++;
    case 2:
        console.log(i);
        i++;
    case 3:
        console.log(i);
        i++;
    case 4:
        console.log(i);
        i++;
    case 5:
        console.log(i);
        i++;
    case 6:
        console.log(i);
        i++;
    case 7:
        console.log(i);
        i++;
    case 8:
        console.log(i);
        i++;
    case 9:
        console.log(i);
        i++;
    case 10:
        console.log(i);
        console.log("Congratulations!");
        break;
    default:
        console.log("Buzz, wronghh");
        break;
}

I just learned switch statements. I was practicing it by building something. When i set the value of variable to a number it works but when i asks the user for a number it always outputs the default statement.

It works with this code:

confirm("You want to learn basic counting?");
var i = 0;
switch (i) {
    case 0:
        console.log(i);
        i++
    case 1:
        console.log(i);
        i++;
    case 2:
        console.log(i);
        i++;
    case 3:
        console.log(i);
        i++;
    case 4:
        console.log(i);
        i++;
    case 5:
        console.log(i);
        i++;
    case 6:
        console.log(i);
        i++;
    case 7:
        console.log(i);
        i++;
    case 8:
        console.log(i);
        i++;
    case 9:
        console.log(i);
        i++;
    case 10:
        console.log(i);
        console.log("Congratulations!");
        break;
    default:
        console.log("Buzz, wronghh");
        break;
}

But when i asks value from user, it dosen't work. Code below doesn't work:

confirm("You want to learn basic counting?");
var i = prompt("Type any number from where you want to start counting[Between 0 and 10]");
switch (i) {
    case 0:
        console.log(i);
        i++
    case 1:
        console.log(i);
        i++;
    case 2:
        console.log(i);
        i++;
    case 3:
        console.log(i);
        i++;
    case 4:
        console.log(i);
        i++;
    case 5:
        console.log(i);
        i++;
    case 6:
        console.log(i);
        i++;
    case 7:
        console.log(i);
        i++;
    case 8:
        console.log(i);
        i++;
    case 9:
        console.log(i);
        i++;
    case 10:
        console.log(i);
        console.log("Congratulations!");
        break;
    default:
        console.log("Buzz, wronghh");
        break;
}

• javascript
• syntax
• switch-statement
• prompt

Share Improve this question Follow edited Jul 28, 2015 at 8:14 Salman Arshad 272k8484 gold badges443443 silver badges534534 bronze badges asked Jul 27, 2015 at 20:13 LaviosLavios 1,1791010 silver badges2222 bronze badges 0

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3 Answers 3

Sorted by: Reset to default 9

You need to convert the user input from a string to an integer, like so

confirm("You want to learn basic counting?");
var i = prompt("Type any number from where you want to start counting[Between 0 and 10]");
i = parseInt(i); // this makes it an integer
switch(i) {
//...

The switch statement performs a strict parison between the input expression and case expressions. The output of the following would be:

var i = 1;
switch (i) {
    case "1":
        console.log('String 1');
        break;
    case 1:
        console.log('Number 1');
        break;
}
// Number 1

var j = "1";
switch (j) {
    case "1":
        console.log('String 1');
        break;
    case 1:
        console.log('Number 1');
        break;
}
// String 1

The prompt function returns a string so either:

• Change your case statements to case "1":, case "2":
• Case the user input to a number using i = Number(i)

Besides other answers, you can use the unary plus +. It actually does the same thing as Number(...), but is shorter. In other words, the plus operator + applied to a single value, doesn’t do anything to numbers. But if the operand is not a number, the unary plus converts it into a number.

for instance:

let a = '2';
alert( a + 3); // 23

but

let a = '2';
alert( +a + 3); // 5

so add unary + before prompt in your code:

var i = +prompt("Type any number from where you want to start counting[Between 0 and 10]");

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