nouislider.js

                to = scope_Values[handleNumber] + step;
            } else if (isMax) {
                // End key
                to = options.spectrum.xVal[options.spectrum.xVal.length - 1];
            } else {
                // Home key
                to = options.spectrum.xVal[0];
            }

            setHandle(handleNumber, scope_Spectrum.toStepping(to), true, true);

            fireEvent("slide", handleNumber);
            fireEvent("update", handleNumber);
            fireEvent("change", handleNumber);
            fireEvent("set", handleNumber);

            return false;
        }

        // Attach events to several slider parts.
        function bindSliderEvents(behaviour) {
            // Attach the standard drag event to the handles.
            if (!behaviour.fixed) {
                scope_Handles.forEach(function(handle, index) {
                    // These events are only bound to the visual handle
                    // element, not the 'real' origin element.
                    attachEvent(actions.start, handle.children[0], eventStart, {
                        handleNumbers: [index]
                    });
                });
            }

            // Attach the tap event to the slider base.
            if (behaviour.tap) {
                attachEvent(actions.start, scope_Base, eventTap, {});
            }

            // Fire hover events
            if (behaviour.hover) {
                attachEvent(actions.move, scope_Base, eventHover, {
                    hover: true
                });
            }

            // Make the range draggable.
            if (behaviour.drag) {
                scope_Connects.forEach(function(connect, index) {
                    if (connect === false || index === 0 || index === scope_Connects.length - 1) {
                        return;
                    }

                    var handleBefore = scope_Handles[index - 1];
                    var handleAfter = scope_Handles[index];
                    var eventHolders = [connect];

                    addClass(connect, options.cssClasses.draggable);

                    // When the range is fixed, the entire range can
                    // be dragged by the handles. The handle in the first
                    // origin will propagate the start event upward,
                    // but it needs to be bound manually on the other.
                    if (behaviour.fixed) {
                        eventHolders.push(handleBefore.children[0]);
                        eventHolders.push(handleAfter.children[0]);
                    }

                    eventHolders.forEach(function(eventHolder) {
                        attachEvent(actions.start, eventHolder, eventStart, {
                            handles: [handleBefore, handleAfter],
                            handleNumbers: [index - 1, index]
                        });
                    });
                });
            }
        }

        // Attach an event to this slider, possibly including a namespace
        function bindEvent(namespacedEvent, callback) {
            scope_Events[namespacedEvent] = scope_Events[namespacedEvent] || [];
            scope_Events[namespacedEvent].push(callback);

            // If the event bound is 'update,' fire it immediately for all handles.
            if (namespacedEvent.split(".")[0] === "update") {
                scope_Handles.forEach(function(a, index) {
                    fireEvent("update", index);
                });
            }
        }

        // Undo attachment of event
        function removeEvent(namespacedEvent) {
            var event = namespacedEvent && namespacedEvent.split(".")[0];
            var namespace = event && namespacedEvent.substring(event.length);

            Object.keys(scope_Events).forEach(function(bind) {
                var tEvent = bind.split(".")[0];
                var tNamespace = bind.substring(tEvent.length);

                if ((!event || event === tEvent) && (!namespace || namespace === tNamespace)) {
                    delete scope_Events[bind];
                }
            });
        }

        // External event handling
        function fireEvent(eventName, handleNumber, tap) {
            Object.keys(scope_Events).forEach(function(targetEvent) {
                var eventType = targetEvent.split(".")[0];

                if (eventName === eventType) {
                    scope_Events[targetEvent].forEach(function(callback) {
                        callback.call(
                            // Use the slider public API as the scope ('this')
                            scope_Self,
                            // Return values as array, so arg_1[arg_2] is always valid.
                            scope_Values.map(options.format.to),
                            // Handle index, 0 or 1
                            handleNumber,
                            // Un-formatted slider values
                            scope_Values.slice(),
                            // Event is fired by tap, true or false
                            tap || false,
                            // Left offset of the handle, in relation to the slider
                            scope_Locations.slice(),
                            // add the slider public API to an accessible parameter when this is unavailable
                            scope_Self
                        );
                    });
                }
            });
        }

        // Split out the handle positioning logic so the Move event can use it, too
        function checkHandlePosition(reference, handleNumber, to, lookBackward, lookForward, getValue) {
            var distance;

            // For sliders with multiple handles, limit movement to the other handle.
            // Apply the margin option by adding it to the handle positions.
            if (scope_Handles.length > 1 && !options.events.unconstrained) {
                if (lookBackward && handleNumber > 0) {
                    distance = scope_Spectrum.getAbsoluteDistance(reference[handleNumber - 1], options.margin, 0);
                    to = Math.max(to, distance);
                }

                if (lookForward && handleNumber < scope_Handles.length - 1) {
                    distance = scope_Spectrum.getAbsoluteDistance(reference[handleNumber + 1], options.margin, 1);
                    to = Math.min(to, distance);
                }
            }

            // The limit option has the opposite effect, limiting handles to a
            // maximum distance from another. Limit must be > 0, as otherwise
            // handles would be unmovable.
            if (scope_Handles.length > 1 && options.limit) {
                if (lookBackward && handleNumber > 0) {
                    distance = scope_Spectrum.getAbsoluteDistance(reference[handleNumber - 1], options.limit, 0);
                    to = Math.min(to, distance);
                }

                if (lookForward && handleNumber < scope_Handles.length - 1) {
                    distance = scope_Spectrum.getAbsoluteDistance(reference[handleNumber + 1], options.limit, 1);
                    to = Math.max(to, distance);
                }
            }

            // The padding option keeps the handles a certain distance from the
            // edges of the slider. Padding must be > 0.
            if (options.padding) {
                if (handleNumber === 0) {
                    distance = scope_Spectrum.getAbsoluteDistance(0, options.padding[0], 0);
                    to = Math.max(to, distance);
                }

                if (handleNumber === scope_Handles.length - 1) {
                    distance = scope_Spectrum.getAbsoluteDistance(100, options.padding[1], 1);
                    to = Math.min(to, distance);
                }
            }

            to = scope_Spectrum.getStep(to);

            // Limit percentage to the 0 - 100 range
            to = limit(to);

            // Return false if handle can't move
            if (to === reference[handleNumber] && !getValue) {
                return false;
            }

            return to;
        }

        // Uses slider orientation to create CSS rules. a = base value;
        function inRuleOrder(v, a) {
            var o = options.ort;
            return (o ? a : v) + ", " + (o ? v : a);
        }

        // Moves handle(s) by a percentage
        // (bool, % to move, [% where handle started, ...], [index in scope_Handles, ...])
        function moveHandles(upward, proposal, locations, handleNumbers) {
            var proposals = locations.slice();

            var b = [!upward, upward];
            var f = [upward, !upward];

            // Copy handleNumbers so we don't change the dataset
            handleNumbers = handleNumbers.slice();

            // Check to see which handle is 'leading'.
            // If that one can't move the second can't either.
            if (upward) {
                handleNumbers.reverse();
            }

            // Step 1: get the maximum percentage that any of the handles can move
            if (handleNumbers.length > 1) {
                handleNumbers.forEach(function(handleNumber, o) {
                    var to = checkHandlePosition(
                        proposals,
                        handleNumber,
                        proposals[handleNumber] + proposal,
                        b[o],
                        f[o],
                        false
                    );

                    // Stop if one of the handles can't move.
                    if (to === false) {
                        proposal = 0;
                    } else {
                        proposal = to - proposals[handleNumber];
                        proposals[handleNumber] = to;
                    }
                });
            }

            // If using one handle, check backward AND forward
            else {
                b = f = [true];
            }

            var state = false;

            // Step 2: Try to set the handles with the found percentage
            handleNumbers.forEach(function(handleNumber, o) {
                state = setHandle(handleNumber, locations[handleNumber] + proposal, b[o], f[o]) || state;
            });

            // Step 3: If a handle moved, fire events
            if (state) {
                handleNumbers.forEach(function(handleNumber) {
                    fireEvent("update", handleNumber);
                    fireEvent("slide", handleNumber);
                });
            }
        }

        // Takes a base value and an offset. This offset is used for the connect bar size.
        // In the initial design for this feature, the origin element was 1% wide.
        // Unfortunately, a rounding bug in Chrome makes it impossible to implement this feature
        // in this manner: https://bugs.chromium.org/p/chromium/issues/detail?id=798223
        function transformDirection(a, b) {
            return options.dir ? 100 - a - b : a;
        }

        // Updates scope_Locations and scope_Values, updates visual state
        function updateHandlePosition(handleNumber, to) {
            // Update locations.
            scope_Locations[handleNumber] = to;

            // Convert the value to the slider stepping/range.
            scope_Values[handleNumber] = scope_Spectrum.fromStepping(to);

            var translation = 10 * (transformDirection(to, 0) - scope_DirOffset);
            var translateRule = "translate(" + inRuleOrder(translation + "%", "0") + ")";

            scope_Handles[handleNumber].style[options.transformRule] = translateRule;

            updateConnect(handleNumber);
            updateConnect(handleNumber + 1);
        }

        // Handles before the slider middle are stacked later = higher,
        // Handles after the middle later is lower
        // [[7] [8] .......... | .......... [5] [4]
        function setZindex() {
            scope_HandleNumbers.forEach(function(handleNumber) {
                var dir = scope_Locations[handleNumber] > 50 ? -1 : 1;
                var zIndex = 3 + (scope_Handles.length + dir * handleNumber);
                scope_Handles[handleNumber].style.zIndex = zIndex;
            });
        }

        // Test suggested values and apply margin, step.
        function setHandle(handleNumber, to, lookBackward, lookForward) {
            to = checkHandlePosition(scope_Locations, handleNumber, to, lookBackward, lookForward, false);

            if (to === false) {
                return false;
            }

            updateHandlePosition(handleNumber, to);

            return true;
        }

        // Updates style attribute for connect nodes
        function updateConnect(index) {
            // Skip connects set to false
            if (!scope_Connects[index]) {
                return;
            }

            var l = 0;
            var h = 100;

            if (index !== 0) {
                l = scope_Locations[index - 1];
            }

            if (index !== scope_Connects.length - 1) {
                h = scope_Locations[index];
            }

            // We use two rules:
            // 'translate' to change the left/top offset;
            // 'scale' to change the width of the element;
            // As the element has a width of 100%, a translation of 100% is equal to 100% of the parent (.noUi-base)
            var connectWidth = h - l;
            var translateRule = "translate(" + inRuleOrder(transformDirection(l, connectWidth) + "%", "0") + ")";
            var scaleRule = "scale(" + inRuleOrder(connectWidth / 100, "1") + ")";

            scope_Connects[index].style[options.transformRule] = translateRule + " " + scaleRule;
        }

        // Parses value passed to .set method. Returns current value if not parse-able.
        function resolveToValue(to, handleNumber) {
            // Setting with null indicates an 'ignore'.
            // Inputting 'false' is invalid.
            if (to === null || to === false || to === undefined) {
                return scope_Locations[handleNumber];
            }

            // If a formatted number was passed, attempt to decode it.
            if (typeof to === "number") {
                to = String(to);
            }

            to = options.format.from(to);
            to = scope_Spectrum.toStepping(to);

            // If parsing the number failed, use the current value.
            if (to === false || isNaN(to)) {
                return scope_Locations[handleNumber];
            }

            return to;
        }

        // Set the slider value.
        function valueSet(input, fireSetEvent) {
            var values = asArray(input);
            var isInit = scope_Locations[0] === undefined;

            // Event fires by default
            fireSetEvent = fireSetEvent === undefined ? true : !!fireSetEvent;

            // Animation is optional.
            // Make sure the initial values were set before using animated placement.
            if (options.animate && !isInit) {
                addClassFor(scope_Target, options.cssClasses.tap, options.animationDuration);
            }

            // First pass, without lookAhead but with lookBackward. Values are set from left to right.
            scope_HandleNumbers.forEach(function(handleNumber) {
                setHandle(handleNumber, resolveToValue(values[handleNumber], handleNumber), true, false);
            });

            var i = scope_HandleNumbers.length === 1 ? 0 : 1;

            // Secondary passes. Now that all base values are set, apply constraints.
            // Iterate all handles to ensure constraints are applied for the entire slider (Issue #1009)
            for (; i < scope_HandleNumbers.length; ++i) {
                scope_HandleNumbers.forEach(function(handleNumber) {
                    setHandle(handleNumber, scope_Locations[handleNumber], true, true);
                });
            }

            setZindex();

            scope_HandleNumbers.forEach(function(handleNumber) {
                fireEvent("update", handleNumber);

                // Fire the event only for handles that received a new value, as per #579
                if (values[handleNumber] !== null && fireSetEvent) {
                    fireEvent("set", handleNumber);
                }
            });
        }

        // Reset slider to initial values
        function valueReset(fireSetEvent) {
            valueSet(options.start, fireSetEvent);
        }

        // Set value for a single handle
        function valueSetHandle(handleNumber, value, fireSetEvent) {
            // Ensure numeric input
            handleNumber = Number(handleNumber);

            if (!(handleNumber >= 0 && handleNumber < scope_HandleNumbers.length)) {
                throw new Error("noUiSlider (" + VERSION + "): invalid handle number, got: " + handleNumber);
            }

            // Look both backward and forward, since we don't want this handle to "push" other handles (#960);
            setHandle(handleNumber, resolveToValue(value, handleNumber), true, true);

            fireEvent("update", handleNumber);

            if (fireSetEvent) {
                fireEvent("set", handleNumber);
            }
        }

        // Get the slider value.
        function valueGet() {
            var values = scope_Values.map(options.format.to);

            // If only one handle is used, return a single value.
            if (values.length === 1) {
                return values[0];
            }

            return values;
        }

        // Removes classes from the root and empties it.
        function destroy() {
            for (var key in options.cssClasses) {
                if (!options.cssClasses.hasOwnProperty(key)) {
                    continue;
                }
                removeClass(scope_Target, options.cssClasses[key]);
            }

            while (scope_Target.firstChild) {
                scope_Target.removeChild(scope_Target.firstChild);
            }

            delete scope_Target.noUiSlider;
        }

        function getNextStepsForHandle(handleNumber) {
            var location = scope_Locations[handleNumber];
            var nearbySteps = scope_Spectrum.getNearbySteps(location);
            var value = scope_Values[handleNumber];
            var increment = nearbySteps.thisStep.step;
            var decrement = null;

            // If snapped, directly use defined step value
            if (options.snap) {
                return [
                    value - nearbySteps.stepBefore.startValue || null,
                    nearbySteps.stepAfter.startValue - value || null
                ];
            }

            // If the next value in this step moves into the next step,
            // the increment is the start of the next step - the current value
            if (increment !== false) {
                if (value + increment > nearbySteps.stepAfter.startValue) {
                    increment = nearbySteps.stepAfter.startValue - value;
                }
            }

            // If the value is beyond the starting point
            if (value > nearbySteps.thisStep.startValue) {
                decrement = nearbySteps.thisStep.step;
            } else if (nearbySteps.stepBefore.step === false) {
                decrement = false;
            }

            // If a handle is at the start of a step, it always steps back into the previous step first
            else {
                decrement = value - nearbySteps.stepBefore.highestStep;
            }

            // Now, if at the slider edges, there is no in/decrement
            if (location === 100) {
                increment = null;
            } else if (location === 0) {
                decrement = null;
            }

            // As per #391, the comparison for the decrement step can have some rounding issues.
            var stepDecimals = scope_Spectrum.countStepDecimals();

            // Round per #391
            if (increment !== null && increment !== false) {
                increment = Number(increment.toFixed(stepDecimals));
            }

            if (decrement !== null && decrement !== false) {
                decrement = Number(decrement.toFixed(stepDecimals));
            }

            return [decrement, increment];
        }

        // Get the current step size for the slider.
        function getNextSteps() {
            return scope_HandleNumbers.map(getNextStepsForHandle);
        }

        // Updateable: margin, limit, padding, step, range, animate, snap
        function updateOptions(optionsToUpdate, fireSetEvent) {
            // Spectrum is created using the range, snap, direction and step options.
            // 'snap' and 'step' can be updated.
            // If 'snap' and 'step' are not passed, they should remain unchanged.
            var v = valueGet();

            var updateAble = [
                "margin",
                "limit",
                "padding",
                "range",
                "animate",
                "snap",
                "step",
                "format",
                "pips",
                "tooltips"
            ];

            // Only change options that we're actually passed to update.
            updateAble.forEach(function(name) {
                // Check for undefined. null removes the value.
                if (optionsToUpdate[name] !== undefined) {
                    originalOptions[name] = optionsToUpdate[name];
                }
            });

            var newOptions = testOptions(originalOptions);

            // Load new options into the slider state
            updateAble.forEach(function(name) {
                if (optionsToUpdate[name] !== undefined) {
                    options[name] = newOptions[name];
                }
            });

            scope_Spectrum = newOptions.spectrum;

            // Limit, margin and padding depend on the spectrum but are stored outside of it. (#677)
            options.margin = newOptions.margin;
            options.limit = newOptions.limit;
            options.padding = newOptions.padding;

            // Update pips, removes existing.
            if (options.pips) {
                pips(options.pips);
            } else {
                removePips();
            }

            // Update tooltips, removes existing.
            if (options.tooltips) {
                tooltips();
            } else {
                removeTooltips();
            }

            // Invalidate the current positioning so valueSet forces an update.
            scope_Locations = [];
            valueSet(optionsToUpdate.start || v, fireSetEvent);
        }

        // Initialization steps
        function setupSlider() {
            // Create the base element, initialize HTML and set classes.
            // Add handles and connect elements.
            scope_Base = addSlider(scope_Target);

            addElements(options.connect, scope_Base);

            // Attach user events.
            bindSliderEvents(options.events);

            // Use the public value method to set the start values.
            valueSet(options.start);

            if (options.pips) {
                pips(options.pips);
            }

            if (options.tooltips) {
                tooltips();
            }

            aria();
        }

        setupSlider();

        // noinspection JSUnusedGlobalSymbols
        scope_Self = {
            destroy: destroy,
            steps: getNextSteps,
            on: bindEvent,
            off: removeEvent,
            get: valueGet,
            set: valueSet,
            setHandle: valueSetHandle,
            reset: valueReset,
            // Exposed for unit testing, don't use this in your application.
            __moveHandles: function(a, b, c) {
                moveHandles(a, b, scope_Locations, c);
            },
            options: originalOptions, // Issue #600, #678
            updateOptions: updateOptions,
            target: scope_Target, // Issue #597
            removePips: removePips,
            removeTooltips: removeTooltips,
            getTooltips: function() {
                return scope_Tooltips;
            },
            getOrigins: function() {
                return scope_Handles;
            },
            pips: pips // Issue #594
        };

        return scope_Self;
    }

    // Run the standard initializer
    function initialize(target, originalOptions) {
        if (!target || !target.nodeName) {
            throw new Error("noUiSlider (" + VERSION + "): create requires a single element, got: " + target);
        }

        // Throw an error if the slider was already initialized.
        if (target.noUiSlider) {
            throw new Error("noUiSlider (" + VERSION + "): Slider was already initialized.");
        }

        // Test the options and create the slider environment;
        var options = testOptions(originalOptions, target);
        var api = scope(target, options, originalOptions);

        target.noUiSlider = api;

        return api;
    }

    // Use an object instead of a function for future expandability;
    return {
        // Exposed for unit testing, don't use this in your application.
        __spectrum: Spectrum,
        version: VERSION,
        // A reference to the default classes, allows global changes.
        // Use the cssClasses option for changes to one slider.
        cssClasses: cssClasses,
        create: initialize
    };
});