50 lines
1.4 KiB
HTML
50 lines
1.4 KiB
HTML
<!DOCTYPE html>
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<html>
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<head>
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<meta charset="utf-8" />
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<meta name="author" content="flykhan" />
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<meta name="keywords" content="c c++ 物联网" />
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<title>JavaScript脚本开发</title>
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<style></style>
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</head>
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<body>
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<script>
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// 字符串类型
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let name = "123"; // 单引号
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let title = "good"; // 双引号
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let age = 29; // 整数
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let score = 125.5; // 小数类型，float
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let content =
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name + "-" + title + ", age is " + age + ", score is " + score;
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alert(content);
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let x = "12",
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y = "45";
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let ret = x * y; // 自动将数字的字符串转成数值
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console.log(ret); // 控制台打印结果 540
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let a = "123";
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let a1 = parseInt(a); // 将 a 转化为 int
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let a2 = Number(a); // 将 a 转化为数值（整数int和小数float）
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console.info(a1);
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console.error(a2); // 会议错误标签打印
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let b = "123abc";
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let b1 = parseInt(b); // 遇到非数字则停止转换
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console.warn(b1);
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let b2 = Number(b); // 如果字符串存在非数字，则返回 NaN （Not a Number）
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console.error(b2);
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let c = "1.25";
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let c1 = parseInt(c); // 遇到小数点结束转换
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let c2 = parseFloat(c);
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let c3 = Number(c); // 可以直接转换为对应数字，如果遇到字母，则返回 NaN
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console.log(c, c1, c2, c3);
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</script>
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</body>
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</html>
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