## 字符串操作 * 獲取字符串的長度 length ~~~ let serverType = "windows"; console.log(serverType.length); ~~~ * 檢索字符，下標從0開始 ~~~ let serverType = "windows"; console.log(serverType[0]); ~~~ * 查找子字符串 ~~~ let serverType = "windows"; console.log(serverType.indexOf("dows"); ~~~ 如果子字符串存在，則會返回第一個字符在原字符串的位置索引；如果不存在則返回-1。 * 截取字符串 ~~~ let serverType = "windows"; console.log(serverType.slice(1,3)); ~~~ * 轉換大小寫 ~~~ let serverType = "Windows"; console.log(serverType.toLowerCase()); console.log(serverType.toUpperCase()); ~~~ * 替換字符串的某部分 ~~~ let serverType = "Windows"; console.log(serverType.replace("dows","dow")); ~~~ * 字符串轉換成數字 ~~~ let myStr = "123"; let myNum = Number(myStr); typeof myNum; ~~~ * 數字轉換成字符串 ~~~ let myNum = 123; let myStr = myNum.toString(); typeof myStr; ~~~