HTML之JavaScript分支结构
if switch
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<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Document</title><script>html" title=javascript>javascript">/*if if(表达式){语句1;}eles if(){语句2;}else{语句3;}1.非空字符串('xxx')会判断为true，空字符('')串会判断为false2.非空对象 会判断为true，null和undefined会判断为false3.非0的number会判断为true，0会判断为falseswitch 跟Java语法一样（跟C语言也没啥逻辑区别）switch(表达式){case 值1:语句1;break;case 值2:语句2;break;case 值3:语句3;break;default:语句4;break;}*/if ("false") {console.log('true');} else {console.log('false');}//根据月份输出季节var month = prompt('请输入月份');//弹窗输入 返回结果为用户在窗口上输入的值，以string类型返回console.log(typeof month);month = Number.parseInt(month);//将字符串转换为数字console.log(typeof month);if (month >= 3 && month <= 5) {console.log('春季');} else if (month == 6 || month == 7 || month == 8) {console.log('夏季');} else if (month == 9 || month == 10 || month == 11) {console.log('秋季');} else if (month == 12 || month == 1 || month == 2) {console.log('冬季');} else {console.log('输入错误');}switch (month) {case 3:case 4://条件穿透 跟Java一样case 5:console.log('春季');break;case 6:case 7:case 8:console.log('夏季');break;case 9:case 10:case 11:console.log('秋季');break;case 12:case 1:case 2:console.log('冬季');break;default:console.log('输入错误');break;}</script>
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