js基础 ---- 事件委托的实战

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>地图栏</title>
</head>

<body>
    <!-- 为 ECharts 准备一个具备大小(宽高)的 DOM -->
    <div id="main" style=" 600px;height:400px;"></div>
    <div style="display: flex;" id='iptBox'>
        美国:<input id="countryA" value=10 /> 日本:
        <input id="countryJ" value=14 /> 中国:
        <input id="countryC" value=18 /> 德国:
        <input id="countryD" value=12 />
    </div>
</body>
<script src="https://cdn.bootcdn.net/ajax/libs/echarts/5.0.1/echarts.common.js"></script>
<script>
    var myChart = echarts.init(document.getElementById('main'));
    var AGDP = document.getElementById('countryA').value;
    var JGDP = document.getElementById('countryJ').value;
    var CGDP = document.getElementById('countryC').value;
    var DGDP = document.getElementById('countryD').value;
    var arrGDP = [AGDP, JGDP, CGDP, DGDP];
    var iptBox = document.getElementById('iptBox');
    var option = {
        title: {
            text: '面试题1'
        },
        tooltip: {

        },
        legend: {
            data: ['GDP']
        },
        xAxis: {},
        yAxis: {
            data: ['美国', '日本', '中国', '德国']
        },
        series: [{
            name: 'GDP',
            type: 'bar',
            data: arrGDP
        }]
    }
    myChart.setOption(option, true)
        //通过事件委托来修input的value值 减少DOM操作来优化性能
    iptBox.addEventListener('change', (e) => {
        let ev = e || window.event;
        console.log(ev.target.id == 'countryA')
        let elId = ev.target.id
        switch (elId) {
            case 'countryA':
                arrGDP[0] = ev.target.value
                break;
            case 'countryJ':
                arrGDP[1] = ev.target.value
                break;
            case 'countryC':
                arrGDP[2] = ev.target.value
                break;
            case 'countryD':
                arrGDP[3] = ev.target.value
                break;
        }
        option.series[0].data = arrGDP
        myChart.setOption(option, true)
    })
</script>

</html>

  

原文地址:https://www.cnblogs.com/qlb-7/p/14523870.html