Question

147

Print value returned by a function to screen in javascript

rated 0 times [ 151] [ 4] / answers: 1 / hits: 68844 / 11 Years ago, sat, march 23, 2013, 12:00:00

I wrote the following JavaScript functions :

<script type=text/javascript>

function showVariable(val){         

    if(typeof(val)!=null && typeof(val)!=false &&typeof(val)!=NaN && typeof(val)!=undefined)

        return typeof(val);

    else 

        return val;

}

function print(){

    var val = {1, 2, 3};

    var res = showVariable(val);

    alert(res);

}

</script>

Currently, I can see the result using alert, but I want to know if there is another method to print showVariable's result in my html document.

Answers

Only authorized users can answer the question. Please sign in first, or register a free account.

peytont

Add To Favorites

Follow

Total Points: 215

Total Questions: 110

Total Answers: 111

Location: Armenia

Member since Sat, Dec 31, 2022

1 Year ago

answered 11 Years ago jimmieo · Accepted Answer

Others have pointed out how to add text to an existing HTML element. A couple other options are described below.

Error log

For debugging, an alternative to alert() that's less intrusive is to add the text to the error log. For instance, in Firefox with the Firebug extension:

if (console.log) console.log(res);

Document.write

Another option that probably won't apply to this particular question, but which is sometimes helpful, is to use document.write. Be careful not to use it after the page has loaded, however, or it will overwrite the page.

For example, the following:

<p>one</p>

<script type=text/javascript>document.write('<p>two</p>');</script>

<p>three</p>

<script type=text/javascript>document.write('<p>four</p>');</script>

Will be displayed in the browser as if the static HTML source code were:

<p>one</p>

<p>two</p>

<p>three</p>

<p>four</p>

typeof

On a side note, the typeof operator returns one of the following string values:

    'undefined'

    'null'          // For browsers that support ECMAScript 6+

    'boolean'

    'number'

    'string'

    'function'

    'object'

The initial if statement could be refactored as follows:

Instead of this               Use this                     Or this

-------------------           -----------------            ------------

typeof(val) != null           val !== null

typeof(val) != false          val !== false

typeof(val) != NaN            typeof val == 'number'       !isNaN(val)

typeof(val) != undefined      typeof val != 'undefined'

Not sure if you need all of those tests though. It depends on what you're trying to do.