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//1.charAt() 查找返回指定位置的字符
var str = "abcdefg";
var s = str.charAt(5); // 下標為5的字符
console.log(s); //f
// 2.charcodeAt()查找返回指定位置字符的unicdoe碼
var str = "abcdefg";
var s = str.charCodeAt(5); // 下標為5的字符的unicdoe碼
console.log(s); //102
// 3.concat()連接字符串
var str = "abc";
var str1 = str.concat("1", "2", "3", "dsdafsdafsad");
console.log(str1); //abc123dsdafsdafsad
// 4.slice()字符串截取
var str = "abcdefghijklmn";
var str1 = str.slice(1, 5);
console.log(str1); //bcde
// 5.split()將字符串轉換為數組
var str = "abcdefg";
var str1 = str.split("-");
var str2 = str.split("");
console.log(str); //abcdefg
console.log(str1); //["abcdefg"]
console.log(str2); //["a", "b", "c", "d", "e", "f", "g"]
// 6.substring()字符串截取
var str = "abcdefghijklm";
var str1 = str.substring(1, 3); //從下邊1開始到下邊3結束, 不包括下標3那一項
var str2 = str.substring(3, 1);
console.log(str1); //bc
console.log(str2); //bc
// 7.substr()字符串截取
var str = "abcdefghijklm";
var str1 = str.substr(2, 6); //從下標2開始往后數6個數
console.log(str1); //cdefgh
// 8.indexOf() 遍歷字符串 查找包含第一個參數的字符串，如包含返回第一位的下標，停止查找，如沒有返回 -1。第二個參數表示從此下標開始查找。
var str = "abcdefabcjklm";
var a = str.indexOf("abc");
var b = str.indexOf("abc", 1);
console.log(a); //0
console.log(b); //6
// 9.toUpperCase 轉大寫
var str = "aAbBcCdD";
console.log(str.toUpperCase()); //AABBCCDD
// 10.toLowerCase 轉小寫
var str = "aAbBcCdD";
console.log(str.toLowerCase()); //aabbccdd
// 11.replace()替換字符串 只能匹配一次
var str = "今天天天天氣好好";
var str1 = str.replace("天天", "**");
console.log(str1); //今**天天氣好好
// 12.match()查找字符串
var str = "今天天氣好好";
var result = str.match("天天");
console.log(result); //["天天", index: 1, input: "今天天氣好好", groups: undefined]
var st = str.match("金");
console.log(st); // null
// 13.search() 查找字符串返回下標
var str = "今天天氣天天好好";
var result = str.search("氣");
console.log(result); //3
var res = str.search("地");
console.log(res); //-1
// 14.startsWith 判定一個字符串是否以另一個字符串開頭
var str = "hello world";
var result = str.startsWith("he");
console.log(result); //true
var result = str.startsWith("he", 1); //當為兩個參數時，第二個表示開始位數。
console.log(result); //flase
// 15.endsWith 判定一個字符串是否以另一個字符串結尾
var str = "hello world";
//檢測尾部
var result = str.endsWith("world");
console.log(result); //true
//檢測指定位置是否以指定字符結尾
var result1 = str.endsWith("wo", 8);
console.log(result1); //true
// 16.includes 檢測是否包含指定字符串
var str = "hello world";
var result = str.includes("o");
console.log(result); //true
var result1 = str.includes("o", 8);
console.log(result1); //false
var res = str.includes("o", 7);
console.log(res); //true
// 17.repeat 重復字符串
var str = "haha";
var str1 = str.repeat(3);
console.log(str1); //hahahahahaha
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