Form with Text Fields - can we show typing before submit?

I am using the PayPal demo form, I have added 2 fields that are lines of text to include on a brick. The people purchase the brick and can customize the text. Is there a way to show the lines of text live on a sample brick (similar to the T-Shirt designer software ) prior to submitting the form? For the brick, I was planning to use just a brick colored div, not a real brick image.
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I tried to set up some javascript-I know it won't do what I want because of the onclick - I need something else- I am not sure what?
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jQuery("input[name='line_1_text']").on('keyup', function() { jQuery('#l1').text(this.val()); });
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Put that in a JS block set to on DOM ready.