Pass string to JavaScript function results in undefined

Question

So what I am trying to do is very simple and straightforward. Passing a String to a JavaScript function and print it as following.

brightRoom('bedroom');

Then

function brightRoom(room){
 console.log("bright " . room);
}

What I get is undefined. Which I am not sure what may caused that issue.

robbmj · Accepted Answer · 2015-03-14 21:48:04Z

1

JavaScript's concatenation operator is a +

brightRoom('bedroom');

function brightRoom(room) {
  // of course console.log("bright " + room); works
  document.write("bright " + room);
}

It results in undefined because the JavaScript engine thinks that you are trying to find a property of the string called room which of course does not exist. When you try to access a non existent property of an object undefined is returned

edited Mar 14, 2015 at 21:48

answered Mar 14, 2015 at 21:29

robbmj

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1 Comment

robbmj Over a year ago

@Abdel-RahmanShoman, no worries, I updated my answer to include why undefined is printed, please have a look.

James · Accepted Answer · 2015-03-14 21:29:46Z

1

Try this

brightRoom('bedroom');

function brightRoom(room){
 console.log("bright " + room);
}

answered Mar 14, 2015 at 21:29

James

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