var str = "Aheloworld";

var str = "Aheloworld";
console.log("str變量中字符串的長(zhǎng)度為："+str.length)

var str = "Aheloworld";
var str1 = str.charAt(3)
console.log("通過(guò)charAt()方法指定下標(biāo)返回字符為："+str1)

var str = "Aheloworld";
var str1 = str.charCodeAt(0)
console.log("通過(guò)charCodeAt()方法指定下標(biāo)返回指定位置的字符的 Unicode 編碼為："+str1)

var str = "Aheloworld";
var str1 = String.fromCharCode(65)
console.log("fromcharcode()指定的 Unicode 值，然后返回一個(gè)字符串"+str1)

var str = "Aheloworld";
var str1 = str.concat("二傻子","三傻子")
console.log("concat() 拼接字符串后的結(jié)果為："+str1)

string.indexOf(searchvalue,start)

var str = "heloworld"
var str1 = str.indexOf("l");
console.log("通過(guò)indexOf()查找指定字符串第一次出現(xiàn)的位置的下標(biāo)："+str1)

var str1 = str.indexOf("l",3);
console.log("通過(guò)indexOf()查找指定字符串規(guī)定字符串查找位置的開(kāi)始地點(diǎn)，返回出現(xiàn)的位置的下標(biāo)："+str1)

var str1 = str.indexOf("l");
console.log("通過(guò)indexOf()查找指定字符串如果字符串不存在，返回-1："+str1)

var str = "abcABCabc"
var str1 = str.lastIndexOf("a")
console.log("通過(guò)lastIndexOf()查找指定字符串最后一次出現(xiàn)的位置的下標(biāo)【從后往前找，下標(biāo)從0往后數(shù)】："+str1)

var str = "abcABCabc"
var str1 = str.slice(1,4)
console.log("slice()方法提取str2字符串中 下標(biāo)1開(kāi)始到下標(biāo)4之前結(jié)束的字符串為："+str1)
var str1 = str.slice(1,-3)// bcABC
var str1 = str.slice(0)//bcABCabc
var str1 = str.slice(-3,-1)//ab
console.log(str1)?? ??? ?

var str = "aocdefghyjklmn"
?? ?// var str1 = str.substring(0,3)
?? ?var str1 = str.substring(4,2)
?? ?console.log(str1)

var str = "aocdefghyjklmn"
var str1 = str.substr(2,3)
var str1 = str.substr(-3,3)
console.log(str1)

var str = "aocdefghyjklmn"
var arr = str.split("")
var arr = str.split("f")
console.log(arr)

var str6 = "abcABC"
console.log("轉(zhuǎn)為大寫(xiě)"+str6.toUpperCase())
console.log("轉(zhuǎn)為小寫(xiě)"+str6.toLowerCase())