1.单分支
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<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>if单分支语句</title>
</head><body><script>if (true) {console.log('小括号是true则执行大括号里的语句，为false则不执行')}if (3 > 5) {console.log('小括号里最终会转换成布尔值来判断')}if (3) {console.log('除了0，所有的字符串都为真')}if ('+3') {console.log('除了空字符串，其余所有字符串都为真')}</script>
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练习:用户输入测试成绩，如果高于700分则通过测试
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<html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>if单分支语句练习</title>
</head><body><script>// 1.用户输入let score = +prompt('请输入测试成绩')// 2.判断if (score >= 700) {alert('恭喜通过测试')}</script>
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