Get thefirstcharacter in a string: lettext ="HELLO WORLD"; letletter = text.charAt(0); Try it Yourself » Get thesecondcharacter in a string: lettext ="HELLO WORLD"; letletter = text.charAt(1); Try it Yourself » Get thelastcharacter in a string: ...
字符串可以是对象 通常, JavaScript 字符串是原始值,可以使用字符创建:var firstName = "John" 但我们也可以使用 new 关键字将字符串定义为一个对象:var firstName = new String("John") 实例 var x = "John"; var y = new String("John"); typeof x // 返回 String typeof y // 返回 Object 尝...
// use template literal let message1 = `This is a long message that spans across multiple lines in the code.`; // use escape character \n // each \n inserts a new line into the string let message2 = "This is a long message
A string can be any text inside double or single quotes: letcarName1 ="Volvo XC60"; letcarName2 ='Volvo XC60'; Try it Yourself » String indexes are zero-based: The first character is in position 0, the second in 1, and so on. ...
first <= 0xDBFF && // high surrogate size > index + 1 // 下一个编码单元 ) { second = string.charCodeAt(index + 1); if (second >= 0xDC00 && second <= 0xDFFF) { // low surrogate // http://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae return (first - 0xD800)...
1、字符串 String 一个字符串用于存储一系列字符就像 "John Doe"。字符串可以使用单引号或双引号 varcarname="Volvo XC60";varcarname='Volvo XC60'; 使用位置(索引,从0开始)可以访问字符串中任何的字符 varcharacter=carname[7]; 可以在字符串中使用引号,或者可以在字符串中使用转义字符( \ )使用引号 ...
//mathiasbynens.be/notes/javascript-encoding#surrogate-formulaereturn(first -0xD800) *0x400+ second -0xDC00+0x10000;}}returnfirst;};if(Object.defineProperty) {Object.defineProperty(String.prototype,'codePointAt', {'value': codePointAt,'configurable':true...
varfirstName ="Bill" ⑵但是字符串也可通过关键词new 定义为对象: varfirstName =newString("Bill") ⑶示例: varx ="John";vary =newString("John");typeofx//返回 Stringtypeofy//返回 Objec 注:不要创建 String 对象。它会拖慢执行速度,并可能产生其他副作用 ...
In JavaScript, first character in the string has position 0, the second one 1, etc. So if you searched for “m”, indexOf method would return 0. If the searched text isn’t found, the method would return -1.Copy if (mailAddress.indexOf("@") == -1) { alert("Character @ wasn...
string – 如果变量是 String 类型的 object – 如果变量是一种引用类型或 Null 类型的 3)通过instanceof 运算符解决引用类型判断问题 4)null 被认为是对象的占位符,typeof运算符对于null值返回“object”。 5)原始数据类型和引用数据类型变量在内存中的存放如下: ...