How to add javascript dynamically to HTML and load it correctly?

Question

I'm trying this: If jQuery is not present, add jQuery dinamically and test it with alert. But this doesn't works, ¿what I'm doing wrong?

HMTL:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">               
<html xmlns="http://www.w3.org/1999/xhtml" xmlns:og="http://ogp.me/ns#" xmlns:fb="http://www.facebook.com/2008/fbml" id="crishk">

<head>
</head>

<body>
    Welcome to Javascript Loader</a>
    <div id="alertme">Alert me!</div>
<script type="text/javascript" language="javascript" src="dynamic.js"></script>
</body>

</html>

File dynamic.js

if (typeof jQuery == 'undefined') {
    alert('You need to install jQuery to proceed.!');

    var oHead = document.getElementsByTagName('head').item(0);
    var oScript = document.createElement("script");
    oScript.type = "text/javascript";
    oScript.src = "http://ajax.googleapis.com/ajax/libs/jquery/1.9.0/jquery.min.js";
    oHead.appendChild(oScript);

} else {
    alert('jQuery is present...');
}
$(document).ready(function () {
    alert($('#alertme').html());
});

But you should load jQuery in your html. The user doesn't need to load it. . . — Michael Peterson
– Michael Peterson, Commented Feb 9, 2013 at 5:29
The load of the jquery API does not occur before the call to $(document).ready(...) which fails because $ has not yet been defined. — Mike Samuel
– Mike Samuel, Commented Feb 9, 2013 at 5:30
1. "load jquery dynamically" - put it to google (I'm wondered you didn't do that yourself) 2. How did you get the totally broken code? Haven't you checked each variable has the expected value? — zerkms
– zerkms, Commented Feb 9, 2013 at 5:31

Sudhanshu Yadav · Accepted Answer · 2013-02-09 05:41:22Z

3

Use onload event to fire functions when jquery being loaded in first if condition. Wrap all other function which require jquery in one function and call it onload of jquery.

this will work for you.

if (typeof jQuery == 'undefined') {
      alert( 'You need to install jQuery to proceed.!');

      var oHead = document.getElementsByTagName('head').item(0);
      var oScript= document.createElement("script");
      oScript.type = "text/javascript";
      oScript.src="http://ajax.googleapis.com/ajax/libs/jquery/1.9.0/jquery.min.js";
      oHead.appendChild( oScript);
        oScript.onload=onload; //on load handler
}
else {
  alert( 'jQuery is present...' );
  onload();
}
function onload(){

alert( $('#alertme').html() );    
};

check http://jsfiddle.net/WVtt9/

answered Feb 9, 2013 at 5:41

Sudhanshu Yadav

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2 Comments

CRISHK Corporation Over a year ago

This works if the code is inside onload() but if you put the code outsite the onload, that doesn't works!! .. you can't use newest codes in other points ...

Sudhanshu Yadav Over a year ago

the other option is to keep all other functions in one file and load they dynamically too.. so your jquery will be loaded first..

CRISHK Corporation · Accepted Answer · 2013-02-18 07:22:36Z

class OutputManager {

    public $output;
    public $dom;
    private $matches;

    function __construct( &$output )
    {
        $this->output = $output;        
        $this->dom = new DOMDocument();
        $this->dom->loadHTML( $this->output );
        $this->dom->normalizeDocument();
        $this->matches = array();
    }

    /**
    * put your comment there...
    * 
    * @param mixed $attr
    * @param mixed $val
    */
    public function elementExists( $tagName, $attr=NULL, $attr_val=NULL )
    {                
        if (count( $this->matches[$tagName] ) == 0) {
            $this->matches[$tagName] = $this->dom->getElementsByTagName( $tagName );
        }

        if ($attr == NULL && $attr_val == NULL) {            
            return $this->matches->length > 0;
        }
        else
        if ($attr != NULL && $attr_val == NULL) {            
            foreach ($this->matches[$tagName] as $match) {
                if ($this->match->hasAttribute($attr))
                    return true;
            }
        }
        else
        if ($attr != NULL && $attr_val != NULL) {
            foreach ($this->matches[$tagName] as $match) {
                if (trim( $match->getAttribute($attr), "/" ) == trim( $attr_val, "/" ))
                    return true;
            }
        }
        return false;
    }

    public function addScript( $src, $at="head" )
    {
        if (!$this->elementExists( "script", "src", $src )) {        

            $result = $this->dom->getElementsByTagName($at);


            $new_script = $this->dom->createElement( "script" );
            $attribute_src = $this->dom->createAttribute( "src" );
            $attribute_src->value = $src;
            $new_script->appendChild( $attribute_src );

            $attribute_type = $this->dom->createAttribute( "type" );
            $attribute_type->value = "text/javascript";
            $new_script->appendChild( $attribute_type );



            $result->item(0)->appendChild( $new_script );

        }
    }

    public function addStylesheet( $href )
    {
        if (!$this->elementExists( "link", "href", $href )) {
            $result = $this->dom->getElementsByTagName($at);

            $new_stylesheet = $this->dom->createElement( "link" );
            $attribute_href = $this->dom->createAttribute( "href" );
            $attribute_href->value = $href;
            $new_stylesheet->appendChild( $attribute_href );

            $attribute_type = $this->dom->createAttribute( "type" );
            $attribute_type->value = "text/css";
            $new_stylesheet->appendChild( $attribute_type );

            $attribute_rel = $this->dom->createAttribute( "rel" );
            $attribute_rel->value = "stylesheet";
            $new_stylesheet->appendChild( $attribute_rel );

            $result->item(0)->appendChild( $new_stylesheet );
        }
    }

    /**
    * Returns the final output.
    * 
    */
    public function getOutput()
    {
        return $this->dom->saveHTML();
    }

    public function getStyles()
    {
        return $matches['link'];
    }

}

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