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passing optional paramaters in javascript/jquery
.load( url [, data] [, complete(responseText, textStatus, XMLHttpRequest)] );

$('#result').load('ajax/test.html', function(){
    alert('Load was performed.');
}

if ( params ) {
    // If it's a function
        if ( jQuery.isFunction( params ) ) {
        // We assume that it's the callback
        callback = params;
        params = null;
    // Otherwise, build a param string
    } else if ( typeof params === "object" ) {
        params = jQuery.param( params, jQuery.ajaxSettings.traditional );
        type = "POST";
    }
}

isFunction: function( obj ) {
    return jQuery.type(obj) === "function";
},
type: function( obj ) {
    return obj == null ?
        String( obj ) :
        class2type[ toString.call(obj) ] || "object";
},

class2type[ "[object Function]" ] = "function";

load: function( url, params, callback ) {

    if (typeof url !== "string" && _load) {
        // My comment: the function.apply ia an
        // alternative way to call a javascript function,
        // where the number of parameter in `arguments`
        // couldn't be determined
        // the `arguments` is a special javascript variable.
        // It's an array containing the parameters within
        // the context of a function
        return _load.apply(this, arguments);

    // Don't do a request if no elements are being requested
    } else if ( !this.length ) {
        return this;
    }

    var off = url.indexOf( " " );
    if ( off >= 0 ) {
        var selector = url.slice( off, url.length );
        url = url.slice( 0, off );
    }

    // Default to a GET request

    var type = "GET";
    // If the second parameter was provided
    if ( params ) {
        // If it's a function
        if ( jQuery.isFunction( params ) ) {
            // We assume that it's the callback
            callback = params;
            params = undefined;
            // Otherwise, build a param string
        } else if ( typeof params === "object" ) {
            params = jQuery.param( params, jQuery.ajaxSettings.traditional );
            type = "POST";
        }
    }

 .... other code

// If the second parameter was provided
    if ( params ) {
        // If it's a function
        if ( jQuery.isFunction( params ) ) {
            // We assume that it's the callback
            callback = params;
            params = undefined;

        // Otherwise, build a param string
        } else if ( typeof params === "object" ) {
            params = jQuery.param( params, jQuery.ajaxSettings.traditional );
            type = "POST";
        }
    }