在javascript中从生成的代码更改文本字符串

var str1 = "Hello";
var str2 = "World";
var result = str1 + " " + str2; // "Hello World"

var str = "Hello";
var len = str.length; // 5

var str = "Hello";
var firstChar = str[0]; // "H"
var lastChar = str[str.length - 1]; // "o"

var str = "Hello World";
var subStr = str.substring(6, 11); // "World"

var str = "Hello World";
var newStr = str.replace("World", "JavaScript"); // "Hello JavaScript"

var str = "Hello";
var upperCaseStr = str.toUpperCase(); // "HELLO"
var lowerCaseStr = str.toLowerCase(); // "hello"

var str = "Hello,World";
var arr = str.split(","); // ["Hello", "World"]