Question

How to prevent draggable child elements from dragging over each other in absolute position?
Something like:

if( ($("#firstChild").position().left) >= ($("#secondChild").position().left) )
{
    $(this).draggable({ disabled: true });
}

but this only disables dragabble when stop dragging, the goal is to prevent from overdragging in some way…Or with Droppable???

Any ideas for CASE 2?

EDIT:

Also, this is maximum for child1 towards child2 , so no overlap occurs, but child1 can push child2 on right, and child2 can push child1 on left, important thing is that no overlap ocurrs!

Answer 1

Some notes before / in order to reach the optimal solution:

• You have declared and initialised the allBetween variablw, but not using it. I suggest to remove it.
• At your #buttonOne event listener, you’re using inconsistent values: 429 and 424: if($("#firstInput").val() > 429 )$("#firstInput").val(424);
  1. You’re using the #firstInput (and #thirdInput) selector multiple times without caching a reference.
  2. You’re duplicating the functions for each button. A better, less error-prone solution is to create a method to build these methods.

Final code

The optimisations have been explained previously. I will not elaborate them, since that’s not the topic of the question. I have explained the function logic of the requested behavior in the scripts comments (below).

$(document).ready(function() {
    // Helper to easily bind related events to the button.
    function createButtonClickEvent(sel_selector, input_selector, left_limit, right_limit) {
        return function(){
            var $sel = $(sel_selector),
                $input = $(input_selector),
                val = $input.val();
            if (val > right_limit) input.val(val = right_limit);
            else if (val < left_limit) input.val(val = left_limit);
            $sel.css('left', val + "px");

            var $allElems = $("#second").children(".single"),
                 $between = $allElems.inRangeX("#selFirst", "#selSecond");
            $allElems.removeClass("ui-selected");
            $between.addClass("ui-selected");
        }
    }
       //setValue 1
    $("#buttonOne").click(createButtonClickEvent("#selFirst", "#firstInput", 0, 429));    
    //setValue2
    $("#buttonTwo").click(createButtonClickEvent("#selSecond", "#thirdInput", 0, 429));


    //graph values
    var valuesG = [],
        $elements = $();
    for (i = 0; i < 144; i++) {
        valuesG[i] = Math.floor(Math.random() * (30 - 20 + 1) + 10);
        $elements = $elements.add($("<div class='single'>")
                             .css('height', valuesG[i])
                             .css('margin-top', 30 - valuesG[i]));
    }
    $elements.appendTo($("#second"));
    $("#second").children(".single").addClass("ui-selected");

    //inRangeX (http://stackoverflow.com/a/8457155/938089)
    (function($) {
        $.fn.inRangeX = function(x1, x2) {

            if (typeof x1 == "string" && +x1 != x1 || x1 instanceof Element) {
                x1 = $(x1);
            }
            if (typeof x2 == "string" && +x1 != x1 || x1 instanceof Element) {
                x2 = $(x2);
            }

            if (x1 instanceof $) {
                x1 = x1.offset().left;
            }
            if (x2 instanceof $) {
                x2 = x2.offset().left;
            }
            x1 = +x1;
            x2 = +x2;


            if (x1 > x2) {
                var x = x1;
                x1 = x2;
                x2 = x;
            }
            return this.filter(function() {
                var $this = $(this),
                    offset = $this.offset(),
                    rightSide = offset.left - 5;
                return offset.left >= x1 + 5 && rightSide <= x2;
            });
        }
    })(jQuery);

    //firstPositions
    var startFirst = $(".selector#selFirst").position().left;
    var startSecond = $(".selector#selSecond").position().left;
    $('input#firstInput').val(startFirst);
    $('input#thirdInput').val(startSecond);

    // *********** Actual requested code *********** //
    //first and second-Picker
    var $selFirst = $("#selFirst"),
        $selSecond = $("#selSecond"),
        cachedWidth = $selFirst.outerWidth();

    function drag_function(event, ui){
        var $firstRightBorder = $selFirst.position().left + cachedWidth,
             $secondLeft = $selSecond.position().left,
             diff = $firstRightBorder - $secondLeft;
        /*
         * The logic is as follows:
         * dif < 0 if selFirst and selSecond do not overlap
         * dif = 0 if they're next to each other
         * dif > 0 if they overlap each other
         * To fix this (reminder: if they overlap, dif is negative):
         * If current == #selFirst,
         *    left = left + dif
         * else (if current == #selSecond),
         *    left = left - dif
         */
        if (diff > 0) {
            var currentLeft = parseFloat($(this).css("left"));
            if (this.id == "selSecond") diff = -diff;
            ui.position.left = currentLeft - diff;
            ui.helper.css("left", currentLeft - diff);
        }
        var $allElems = $("#second").children(".single"),
            $between = $allElems.inRangeX("#selFirst", "#selSecond");
        $("#firstInput").val($("#selFirst").position().left);
        $("#thirdInput").val($("#selSecond").position().left);
        $allElems.removeClass("ui-selected");
        $between.addClass("ui-selected");
        var allBetween = $('.ui-selected');
    }

    $("#selFirst, #selSecond").draggable({
        containment: 'parent',
        axis: 'x',
        drag: drag_function,
        stop: drag_function
    });
}); //eof