如何使用switch语句

Question

im new with JS and i read about the switch statement. i dont know how to use it i got an exercise to complete. got an array with numbers 1-10 and the result need to be with words like "one","two","three".. Thats what i got so far :

function sayNum(){
    let nameNumber = [1,2,3,4,5,6,7,8,9,10]
    let text = '';
    for(let i=0;i<nameNumber.length;i++){
    switch(numbers) {
        case "1":
            text = "one";
            break;
        case "2":
            text = "two";
            break;
        case "3":
            text = "three";
            break;
        case "4":
            text='four';
            break;
        case "5":
            text = "five";
            break;
        case "6":
            text = "six";
            break;
        case "7":
            text = "seven";
            break;
        case "8":
            text = "eight";
            break;
        case "9":
            text = "nine";
            break;
        case "10":
            text = "ten";
    }
    }
    return text;
}
sayNum()

Answer 1

You could do it like this, for example:

function sayNum(){
  let numbers = [1,2,3,4,5,6,7,8,9,10];
  let result = [];

  for(let i=0;i<numbers.length;i++) {
    switch(numbers[i]) {
        case 1:
            text = "one";
            break;
        case 2:
            text = "two";
            break;
        case 3:
            text = "three";
            break;
        case 4:
            text = "four";
            break;
        case 5:
            text = "five";
            break;
        case 6:
            text = "six";
            break;
        case 7:
            text = "seven";
            break;
        case 8:
            text = "eight";
            break;
        case 9:
            text = "nine";
            break;
        case 10:
            text = "ten";
            break;
    }

    result.push(text);
  }

  return result;
}

let namedNumbers = sayNum();
console.info(namedNumbers);

This will:

• Add the textual values to an array, representing each number in the source array
• Return the resulting array to the caller
• Log the result in the console

Answer 2

In the switch statement, you pass an 'expression' into the switch statement. The expression itself can be a string, a number, float, boolean etc. Now, the expression is compared to each of the case clause. And this is a 'strict' comparison. And that is the reason why your code was not working.

Firstly you were passing an undeclared variable, 'numbers' as the switch expression. Instead, you should be passing the ith element of the nameNumber[i] array like so: switch(nameNumber[i]){ }

And, secondly, in each of your case clauses, you are comparing the value to a string like "1", "2". But the switch expression is compared using strict equality === operator, therefore when your nameNumber array contains numbers and not strings, your 'case' clauses should also have numbers and not strings. That means case 1: instead of case "1": .

You can read more about the switch-case here: Switch Statement

I have fixed your code below with the changes I mentioned above. Please run the below code snippet to see how it works. Goodluck!

 function sayNum(){ let nameNumber = [1,2,3,4,5,6,7,8,9,10] let text = ''; for(let i=0;i<nameNumber.length;i++){ switch(nameNumber[i]) { case 1: text = "one"; break; case 2: text = "two"; break; case 3: text = "three"; break; case 4: text='four'; break; case 5: text = "five"; break; case 6: text = "six"; break; case 7: text = "seven"; break; case 8: text = "eight"; break; case 9: text = "nine"; break; case 10: text = "ten"; } console.log(text); } return text; } sayNum();

Answer 3

Rather than using a switch, use if statement. Because in switch, break statement can be used to jump out of a loop.

 let text = ''; function sayNum() { let nameNumber = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]; for (let i = 0; i < nameNumber.length; i++) { if(nameNumber[i] == 1){ text += `"one",`; } if(nameNumber[i] == 2){ text += `"two",`; } if(nameNumber[i] == 3){ text += `"three",`; } if(nameNumber[i] == 4){ text += `"four",`; } if(nameNumber[i] == 5){ text += `"five",`; } if(nameNumber[i] == 6){ text += `"six",`; } if(nameNumber[i] == 7){ text += `"seven",`; } if(nameNumber[i] == 8){ text += `"eight",`; } if(nameNumber[i] == 9){ text += `"nine",`; } if(nameNumber[i] == 10){ text += `"ten"`; } } } sayNum(); console.log(text)