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// Set up the canvas / stage

var stage = new Konva.Stage({container: 'container1', width: 320, height: 180});



// Add a layer

var layer = new Konva.Layer({draggable: false});

stage.add(layer);



// show where the start of the path is.

var circle = new Konva.Circle({

  x: 66,

  y: 15,

  radius: 5,

  stroke: 'red'

 })

 layer.add(circle);



// draw a path.

    var path = new Konva.Path({

      x: 0,

      y: 0,

      data: 'M66 15 L75 100 L225 120 L100 17 L66 15',

      stroke: 'green'

    });



// get the path length and set this as the dash and dashOffset. 

var pathLen = path.getLength();

path.dashOffset(pathLen);

path.dash([pathLen]);



layer.add(path)

stage.draw();



// Some UI bits

$('#dist').attr('max', parseInt(pathLen)); // set slider max to length of path

$('#pathLen').html('Path : ' + pathLen); // display path length



// jquery event listener on slider change

$('#dist').on('input', function(){



  // compute the new dash lenth as original path length - current slider value. 

  // Means that dashLen initially = path len and moves toward zero as slider val increases.

  var dashLen = pathLen - $(this).val();;

  path.dashOffset(dashLen);   // set new value

  layer.draw();               // refresh the layer to see effect



  // update the UI elements      

  $('#dashLen').html('Dash: ' + dashLen);

  $('#pathPC').html(parseInt(100-(100 * (dashLen/pathLen)), 10) + '%');



})

.info 

{

padding-left: 20px;



}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<script src="https://cdnjs.cloudflare.com/ajax/libs/konva/2.5.1/konva.js"></script>

<div class="slidecontainer">

  <input class='slider' id='dist' type="range" min="0" max="100" value="0" class="slider" id="myRange"/>

  <span class='info' id='pathPC'></span>

  <span class='info' id='pathLen'></span>

  <span class='info' id='dashLen'></span>

</div>

<div id='container1' style="display: inline-block; width: 300px, height: 200px; background-color: silver; overflow: hidden; position: relative;"></div>

<div id='img'></div>

    var width = window.innerWidth;

    var height = window.innerHeight;



    // Set up the canvas / stage

    var stage = new Konva.Stage({

        container: 'container',

        width: width,

        height: height

    });



    // Add a layer

    var layer = new Konva.Layer({

        draggable: false

    });

    stage.add(layer);



    // show where the start of the path is.

    var circle = new Konva.Circle({

        x: 66,

        y: 15,

        radius: 5,

        stroke: 'red'

    })

    layer.add(circle);



    // draw a path.

    var path = new Konva.Path({

        x: 0,

        y: 0,

        data: 'M66 15 L75 100 L225 120 L100 17 L66 15',

        stroke: 'green'

    });



    // get the path length and set this as the dash and dashOffset. 

    var pathLen = path.getLength();

    path.dashOffset(pathLen);

    path.dash([pathLen]);



    // make some animation with stop

    var anim = new Konva.Animation(function (frame) {

        var dashLen = pathLen - frame.time / 5;

        path.dashOffset(dashLen);

        if (dashLen < 0) {

            anim.stop();

        }

    }, layer);



    anim.start();



    layer.add(path)

    stage.draw();

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<script src="https://cdnjs.cloudflare.com/ajax/libs/konva/2.5.1/konva.js"></script>

<div id='container' style="display: inline-block; width: 300px, height: 200px; background-color: silver; overflow: hidden; position: relative;"></div>

<div id='img'></div>

var width = window.innerWidth;

    var height = window.innerHeight;



    // Set up the canvas / stage

    var stage = new Konva.Stage({

        container: 'container',

        width: width,

        height: height

    });



    // Add a layer

    var layer = new Konva.Layer({

        draggable: false

    });

    stage.add(layer);



    // show where the start of the path is.

    var circle = new Konva.Circle({

        x: 66,

        y: 15,

        radius: 5,

        stroke: 'red'

    })

    layer.add(circle);



    // draw a path.

    var path = new Konva.Path({

        x: 0,

        y: 0,

        data: 'M66 15 L75 100 L225 120 L100 17 L66 15',

        stroke: 'green'

    });



    // get the path length and set this as the dash and dashOffset. 

    var pathLen = path.getLength();

    path.dashOffset(pathLen);

    path.dash([pathLen]);



    layer.add(path);  // have to add to layer for tweening.

    

    // create the tween

    var tween = new Konva.Tween({

        node: path,

        dashOffset: 0,

        easing: Konva.Easings['BounceEaseOut'],

        duration: 1.5

    });

     tween.play(); // execute the tween



    stage.draw();

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<script src="https://cdnjs.cloudflare.com/ajax/libs/konva/2.5.1/konva.js"></script>

<div id='container' style="display: inline-block; width: 300px, height: 200px; background-color: silver; overflow: hidden; position: relative;"></div>

<div id='img'></div>