JavaScript function that uses switch statement on the type of value - Stack Overflow

admin管理员组

文章数量:1221467

I've been working with the JavaScript learning modules found in CodeAcademy and find myself unredeemed in chapter 4, module 8 (switch - control flow statements)

Please see below for example request:

// Write a function that uses switch statements on the
// type of value. If it is a string, return 'str'. 
// If it is a number, return 'num'. 
// If it is an object, return 'obj'
// If it is anything else, return 'other'.
// compare with the value in each case using ===

and this is what I was able to code:

function StringTypeOf(value) {
var value = true
switch (true) {
 case string === 'string': 
   return "str"; 
   break;
 case number === 'number':
   return "num"; 
   break;
 case object === 'object':
   return "obj"; 
   break;
 default: return "other";
 }
  return value;
}

Can someone please hint or tell me what is missing here?

I've been working with the JavaScript learning modules found in CodeAcademy.com and find myself unredeemed in chapter 4, module 8 (switch - control flow statements)

Please see below for example request:

// Write a function that uses switch statements on the
// type of value. If it is a string, return 'str'. 
// If it is a number, return 'num'. 
// If it is an object, return 'obj'
// If it is anything else, return 'other'.
// compare with the value in each case using ===

and this is what I was able to code:

function StringTypeOf(value) {
var value = true
switch (true) {
 case string === 'string': 
   return "str"; 
   break;
 case number === 'number':
   return "num"; 
   break;
 case object === 'object':
   return "obj"; 
   break;
 default: return "other";
 }
  return value;
}

Can someone please hint or tell me what is missing here?

• javascript

Share Improve this question Follow asked Jan 4, 2012 at 21:23 AlexAlex 37722 gold badges44 silver badges1515 bronze badges 6

• 2 switch( typeof value ) {case "string": ... case "number": ... } – Esailija Commented Jan 4, 2012 at 21:25
• Shouldn't you check for typeof? – PeeHaa Commented Jan 4, 2012 at 21:26
• Hm, I don't know why they tell you to use ===. – Matt Ball Commented Jan 4, 2012 at 21:29
• correction. I was confused about the === comparison. "In a language like Java or C, you can only switch on a few types. In JS, you can switch on anything. The value in the switch statement is compared with the value in each case using ===." – Alex Commented Jan 4, 2012 at 21:34
• @MДΓΓ БДLL : It evaluates the condition faster than when you use the == operator. Because there's no type casting/conversion involved using ===Hence: ("1" === 1) returns false. – Richard A Commented Jan 4, 2012 at 21:35

 |  Show 1 more comment

3 Answers 3

Sorted by: Reset to default 7

You need to use the typeof operator:

var value = true;
switch (typeof value) {
 case 'string': 

function detectType(value) {
  switch (typeof value){
    case 'string':
      return 'str';

    case 'number':
      return 'num';

    case 'object':
      return 'obj';

    default:
      return 'other';
  }
}

you could left out the break; in this case, because is optional after return;

Read the question again - "write a function that uses switch statements on the type of the value". You're missing anything about the type of the value, try using the typeof operator.

typeof "foo" // => "string"
typeof 123 // => "number"
typeof {} // => "object"

本文标签： JavaScript function that uses switch statement on the type of valueStack Overflow