JavaScript學習筆記2—運算子
阿新 • • 發佈:2020-07-23
算術運算子
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title></title> <script type="text/javascript"> /* 運算子也叫操作符 通過運算子可以對一個或多個值進行運算 比如:typeof就是運算子,可以來獲得一個值的型別 它會將該值的型別以字串的形式返回 number string boolean undefined object 算術運算子 當對非Number型別的值進行運算時,會將這些值轉換為Number在進行計算 + +可以對兩個值進行加法運算,並將結果返回 如果對兩個字串進行加法運算,則會做拼串 會將兩個字串拼接為一個字串,並返回 任何的值和字串做加法運算,都會先轉換為字串,然後再和字串做拼串的操作 - -可以對兩個值進行減法運算,並將結果返回 * *可以對兩個值進行乘法運算 / /可以對兩個值進行除法運算 % %取模運算(取餘數)*/ var a = 123; var result = typeof a; console.log(typeof result); a + 1; console.log(a); a = a + 1; console.log(a); a = true + 1; console.log(a); a = true + false; console.log(a); a = 2 + null; console.log(a); a= true + false; console.log(a); a = "123" + "456"; console.log(a); console.log(typeof a); var str = "鋤禾日當午" + "汗滴禾下土" + "誰知盤中餐" + "粒粒皆辛苦"; console.log(str); a = 123 + "1"; console.log(str); a= true + "hello"; console.log(str); //任何值和字串相加都會轉換為字串,並做拼串操作 a = 123 + ""; // a = String(a); console.log(typeof a); console.log(a); a = null; a = a + ""; // a = String(a); console.log(typeof a); console.log(a); a = 123; console.log("a = " + a); a = 1 + 2 + "3";//33 console.log("a = " + a); a = "1" + 2 + 3; console.log("a = " + a); // 減法運算 a = 100 - 5; console.log("a = " + a); a = 100 - true; console.log("a = " + a); a = 100 - "1"; console.log("a = " + a); //乘法運算 a = 2 * 2; console.log("a = " + a); a = 2 * "8"; console.log("a = " + a); a = 2 * undefined; console.log("a = " + a); a = 2 * null; console.log("a = " + a); // 除法運算 a = 3 / 2; console.log("a = " + a); // 任何值做 - * /運算都會自動轉換成Number a = "123"; console.log(typeof a); console.log("a = " + a); // a = Number(a); a = a - 0; a = a * 1; a = a / 1; console.log(typeof a); console.log("a = " + a); // 取餘運算 a = 9 % 3; console.log("a = " + a); </script> </head> <body> </body> </html>