I'm trying to make a markdown editor like Stack Overflow has.

I get this error listed in the title if I don't actually type an asterisk AND a http:// containing phrase into the textarea. If I only type an asterisk containing phrase, the error refers to this line: if(linkify.length!==0)

Here's a jsfiddle to show you what I mean.

Here's my HTML:

<textarea></textarea>

<div></div><button type=button>Markdownify</button>

Here's my JS:

var val=$('textarea').val(), boldify = val.match(/**[A-Za-z0-9]+**/gim),

italicify = val.match(/*[A-Za-z0-9]+*/gim),linkify = val.match(/http://[A-z0-9]+.[A-z0-9]+/gim);



$(document.body).on('click', 'button', function() {



val=$('textarea').val(), boldify = val.match(/**[A-Za-z0-9]+**/gim),

italicify = val.match(/*[A-Za-z0-9]+*/gim),linkify = val.match(/http://[A-z0-9]+.[A-z0-9]+/gim);



if (boldify.length!== 0){

            for (var i=0; i < boldify.length; i++)  {

                var boldMatch= boldify[i],  

                boldReplace = boldMatch.replace(/**[A-z0-9]+**/gim, '<span style=font-weight:bold;color:blue;>'+boldMatch+'</span>'),

                val = val.replace(boldMatch, boldReplace);     

            }

        val = val.replace(/**/gi, );

}



if(italicify.length!== 0){

    for(var j=0; j < italicify.length; j++){

    var italicMatch= italicify[j],

     italicReplace = italicMatch.replace(/*[A-z0-9]+*/gim, '<span style=font-style:italic;color:red;>'+italicMatch+'</span>');

    val = val.replace(italicMatch, italicReplace); 

    }

    val = val.replace(/*/gi, );

}



if(linkify.length!== 0){

    for(var k=0; k < linkify.length; k++){

    var linkMatch= linkify[k],

    linkReplace = linkMatch.replace(/http://[A-z0-9]+.[A-z0-9]+/gim, '<a href='+linkMatch+'>'+linkMatch+'</a>');

        val = val.replace(linkMatch, linkReplace);

    }

}



$('div').html(val);

});

Any help would be greatly appreciated.