JavaScript学习笔记 – 1 – 数据类型和变量
§ 0.1 – JavaScript中的变量种类
- Number类型，代表整数和小数；
- String类型，代表字符串；
- Boolean类型，代表二元逻辑真伪；
§ 0.2 – JavaScript中的返回值种类
- Undefined类型，代表未赋值（未知类型）的变量；
- Null类型，代表已经赋值但是值为空（empty）的变量；
- NaN（Not a Number）类型，表示“非数字”，通常返回NaN表示数字运算存在错误；
§ 1.0 – Number类型变量
1.1 变量声明
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// Variable Types - Number var number = 1; console.log(number); |
§ 2.0 – String类型变量
2.1 变量声明
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// Variable Types - String var firstString = "This is a String."; var secondString = "This is another String."; |
2.2 字符串连接
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// Concatenation of String console.log(firstString + " " + secondString); // results "This is a String. This is another String." |
2.3 字符串索引
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// Index of String console.log(firstString[0]); // results "T" |
2.4 字符串中的特殊符号转义
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// Escape String/special Char with "\" console.log("\"C:\\\\Desktop\\My Documents\\Roster\\names.txt\""); // Newline with "\n" console.log("Nice to meet you!\nNice to meet you, too!"); // New tab with "\t" console.log("Nice to meet you!\tNice to meet you, too!"); |
2.5 字符串比较
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/* Compare of Strings ------------------ When checking if a string is "greater than" or "less than" another string, JavaScript compares individual characters using a numerical value. Each character is assigned a numerical value that essentially corresponds to the character's location in an ASCII Lowercase letters have higher numerical values in the ASCII table than uppercase letters. */ console.log("Green" > "Blue"); // returns true console.log("Green" > "green"); // returns false console.log("green" > "Green"); // returns true |
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