D3 update bar data on click

CSS

body {
	     padding: 30px;
	     background: #000;
	 }
	 rect {
	     fill: purple;
	     padding: 7px;
	     margin: 2px;
	     color: white;
	 }
	 rect:hover {
	     opacity : 0.5;
	 }

JavaScript

var w = 500;
var h = 100;
var barPadding = 1;

var dataset = [5, 10, 13, 19, 21, 25, 22, 18, 15, 13,
11, 12, 15, 20, 18, 17, 16, 18, 23, 25];

//Create SVG element
var svg = d3.select("body")
    .append("svg")
    .attr("width", w)
    .attr("height", h);

function render() {
    var bars = svg.selectAll("rect")
        .data(dataset);
    
    bars.enter()
        .append("rect");
    
    bars.on("click", clickEvent)
        .attr("x", function (d, i) {
            return i * (w / dataset.length);
        })
        .attr("y", function (d) {
            return h - (d * 4);
        })
         .transition()
		    .duration(1500)
        .attr("width", w / dataset.length - barPadding)
        .attr("height", function (d) {
            return d * 4;
        });
};
render();

function clickEvent(d, i) {
    var op = prompt("Please enter the value", d);
    dataset[i] = parseInt(op, 10);
    render();
};