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javascriptswitch-statementcase
Emile
Emile

Reputation: 33

Javascript switch with string variable not working

Could anyone tell me why the below switch is not working?

var String=new String('String #1');

document.write(String);

document.write(' Check ');

switch(String)
{

    case 'String #1' : 
    document.write('String Number 1');
    break;
    default: document.write('wrong string');
}

The output is: String #1 Check wrong string

Upvotes: 3

Views: 13915

Answers (4)

Raff
Raff

Reputation: 61

Another simple solution is to concat a primitive string and your string object. The result is a primitive string, which can be used in a switch statement.

var String=new String('String #1');

document.write(String);

document.write(' Check ');

switch('' + String)
{

    case 'String #1' : 
    document.write('String Number 1');
    break;
    default: document.write('wrong string');
}

Upvotes: 0

Andrew Li
Andrew Li

Reputation: 57964

String is a constructor that's builtin to JavaScript. Naming variables that shadow these constructors will cause an error:

TypeError: String is not a constructor

Rename the String variable and do not use the switch statement here because you have a String instance. switch statements use strict comparison (===) per the MDN documentation and the ECMAScript 2015 specification. Since a string instance and literal are never 'strictly equal', comparison fails. Don't instantiate, instead use a literal:

var string = "String #1";

switch(string) {
  case "String #1":
    document.write("String Number 1");
    break;
  default: 
    document.write("wrong string");
}

Also, I don't recommend using document.write, see here. Logging or inserting into the DOM with createElement and appendChild should work sufficiently here.

Upvotes: 4

Adam Buchanan Smith
Adam Buchanan Smith

Reputation: 9457

You can change the object to a string using toString() See example https://jsfiddle.net/DIRTY_SMITH/59x9xn3g/1/

<script>
var someObject =new String('String #1');
var someString = someObject.toString();
document.write(someString);

document.write(' Check ');

switch(someString)
{

    case 'String #1' : document.write('String Number 1');
    break;
    default: document.write('wrong string');
}
</script>

Upvotes: 2

kevin ternet
kevin ternet

Reputation: 4612

You must compare an Object with an Object not a String with an Object. Here I compare an object with an Object :

var string = "String #1";
console.log(string);
console.log("Check");

switch(string)
{
    case "String #1":
    console.log("String Number 1");
    break;
    default: console.log("wrong string");
}

Upvotes: 3

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