.delay（）不是d3中的函数

Question

So far the only library I have imported is d3, and I checked the d3.js file to make sure the function was there. It was.

I'm trying to do the example from the data visualization with D3 and AngularJS book. Here's the code [directly from the book, with comments removed] in question:

<svg width="800" height="500"></svg>
<script type="text/javascript">
var data = [];
setInterval(function(){
    if (data.length < 8) {
        data.push(Math.random());
    }
    else {
        data = [];
    }
    draw();
}, 1000);

function draw() {
    var svg = d3.select('svg');

    var circles = svg.selectAll('circle').data(data);

    circles
    .attr('fill', 'orange');

    circles.enter()
    .append('circle')
    .attr('fill', 'red')
    .attr('r', 40)
    .attr('cx', function(d, i) { return i*100 + 50; })
    .attr('cy', 50);

    circles
    .style('stroke', 'black');

    circles.exit()
    .delay()
    .remove();
}

The problem I am having specifically is at

circles
.exit()
.delay()
.remove();

It says that the delay function "is not a function" even though it is. I tried porting the code exactly from the book into a completely new project, but it doesn't work. (I'm using the chrome browser if that makes a difference).

Thanks

Answer 1

delay() is not a function of selections . You can call delay() for transitions, however. So :

circles
  .exit()
  .transition()
  .delay()
  .remove();