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jquerymathjax

Recognize when writing in between two $$ signs

I have a textfield in which I'm writing some text.

For the sake of simplicity, I want that alert('Boom!') jumps out every time I start writing in between two $$.

For example I have a blank textfield and start typing (cursor is "|" sign)

Today is a really nice day|

nothing happens, start typing

Today is a really nice day, $|$

still nothing, but now when I start typing

Today is a really nice day, $someText|$

alert box should jump out for each letter in between those dollar signs.

Why do I need that kind of feature? I want live-equation-preview (MathJax rendering) every time user starts typing his/her equation, and I can recognize it's an equation by $$ signs (everything in between is rendered).

EDIT: Multiple $$'s are possible in textfield. Script must recognize the one which is currently active (cursor position is between it's $$'s).

Solution

  • You can use jQuery caret plugin

    http://examplet.buss.hk/download/download.php?plugin=caret.1.01

    note: edit and delete these characters Ôªø from line 8

    and replace funcition. ( not to replace anything but to use the index of matched pattern )

    $("#myText").bind("keyup", function(e){
     var text = $(this).val();
     var caret = $(this).caret().start;

     if(text && text.length > 0){
        text.replace(/\$.*?\$/g, function(m, n){
           if(caret > n && caret < (n + m.length)){
              alert("BOOM");
           }
        });
     }
});

    demo : http://jsfiddle.net/xqXXb/

    Just showing how to do it. You can improve this.

    use

    $("#myText").bind("keyup keydown change", function(e){ ...

    for a better result.