Question

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Can someone explain the dollar sign in Javascript?

Why do certain javascript functions have a $ before the function delcaration?
For example, here’s the javascript for a JQuery slider. The source code can be found here http://jqueryui.com/slider/#rangemin

<script>
$(function() {
    $( "#slider-range-min" ).slider({
        range: "min",
        value: 37,
        min: 1,
        max: 700,
        slide: function( event, ui ) {
            $( "#amount" ).val( "$" + ui.value );
        }
    });
    $( "#amount" ).val( "$" + $( "#slider-range-min" ).slider( "value" ) );
});
</script>

Answer 1

The $ isn’t a JavaScript thing, it’s just a shortcut used by jQuery. $ is a valid identifier name in JavaScript, and it’s short, so it was popular with libraries (jQuery, Prototype, and probably a couple of others used it). $ is just an alias for the symbol jQuery.

The code you’ve quoted there is calling the $ function and passing in a function reference (in this case, for a function defined inline). When you pass a function reference into $ (or jQuery), you’re asking the jQuery library to run that function when the DOM is ready. It’s a shortcut for $(document).ready(...). Details in the documentation.