Switch Statement, it does not work with prompt

问题

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;
}

回答1:

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) {
//...

回答2:

The switch statement performs a strict comparison 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)

来源：https://stackoverflow.com/questions/31662389/switch-statement-it-does-not-work-with-prompt

标签

javascript

syntax

switch-statement

prompt