字符串的常用属性和方法

字符串的常用属性和方法

一.常用属性

1. length获取字符串的长度

let txt = "Hello js!";
console.log(txt.length); -------> 9

二.常用方法

• String的对象方法

1. charAt()根据索引获取索引对应的字符

let txt = "Hello js!";
console.log(txt.charAt(4)); ------> o

2. charCodeAt()

let txt = "Hello js!";
console.log(txt.charCodeAt(4));------>111

3. concat()连接字符串

let txt = "Hello js!";
console.log(txt.concat(111));------>Hello js!111

4. fromCharCode()将 Unicode编码转为字符

String.fromCharCode(72,69,76,76,111);----->HELLo

5. indexOf和lastIndexOf

   ​ indexOf：获取字符第一次出现在字符串里面的索引

   ​ lastIndexOf ：获取字符最后一次出现在字符串里面的索引

let txt = "Hello js!";
console.log(txt.indexOf('l')); ------>2
console.log(txt.lastIndexOf('l')); ------>3

6. includes()判断字符串里面是否包含匹配的子字符串

let txt = "Hello js!";
console.log(txt.includes('l')) ------>true
console.log(txt.includes('lp'))------->false

7. match()查找找到一个或多个正则表达式的匹配

var str="The rain in SPAIN stays mainly in the plain"; 
console.log(str.match(/in/g));------>["in", "in", "in", "in", "in"]

​ 8.repeat()复制字符串指定次数，并将它们连接在一起返回

let txt = "Hello js!";
console.log(txt.repeat(2)) ----->Hello js!Hello js!

9. search()查找相匹配的子字符串的开始下边。

let txt="my name is blue";
txt.search("blue"); ----->11

11. slice()提取字符串的片断，并在新的字符串中返回被提取的部分

let txt="my name is blue";
txt.slice(1,5); ----->y na

11. split()把字符串分割为字符串数组

let txt="my name is blue";
txt.split(" ");------["my", "name", "is", "blue"]

12. startsWith()和endsWith()

    startsWith()：查看字符串是否以指定的子字符串开头

    endsWith()：查看字符串是否以指定的子字符串结束

let txt="my name is blue";
txt.startsWith("my") ------> true
txt.endsWith("my") ------> false

13. substr()和substring()

    substr()：从起始索引号提取字符串中指定数目的字符

    substring()：提取字符串中两个指定的索引号之间的字符

let txt="my name is blue";
txt.substr(3,4) ------> 'name'
txt.substring(3.4) ------> 'ns'

14. toLowerCase()和toUpperCase()

    toLowerCase()：把字符串里面的大写字母变成小写

    toUpperCase()：把字符串里面的小写字母变成大写

let txt="My Name Is Blue";
txt.toLowerCase() ------> 'my name is blue'
txt.toUpperCase() ------> 'MY NAME IS BLUE'

15. trim()去除字符串两边的空格

let txt=" My Name Is Blue ";
txt.trim()---->'My Name Is Blue'

16. replace()在字符串中查找匹配的子串， 并替换与正则表达式匹配的子串

let txt="My Name Is Blue";
txt.replace("My",222)------>'222 Name Is Blue'

• HTML标签包裹着的内容(需要看浏览器的支持力度)

let txt = "Hello js!";
document.write("<p>字体变大: " + txt.big() + "</p>");
document.write("<p>字体缩小: " + txt.small() + "</p>");
document.write("<p>字体加粗: " + txt.bold() + "</p>");
document.write("<p>斜体: " + txt.italics() + "</p>");
document.write("<p>固定定位: " + txt.fixed() + "</p>");
document.write("<p>加删除线: " + txt.strike() + "</p>");
document.write("<p>字体颜色: " + txt.fontcolor("green") + "</p>");
document.write("<p>字体大小: " + txt.fontsize(6) + "</p>");
document.write("<p>下标: " + txt.sub() + "</p>");
document.write("<p>上标: " + txt.sup() + "</p>");
document.write("<p>链接: " + txt.link("http://www.w3cschool.cc") + "</p>");
document.write("<p>闪动文本: " + txt.blink() + "</p>");

​ 效果如下图：