Detailed explanation of js expressions and operator codes

/** * Created by Administrator on 2017/12/14. * 表达式与运算符 */ //1.基本表达式 加减乘除 var a = 4; a = 7/6; var b = (a + 4)/2; console.log(a); console.log(b); console.log("=========="); //end //2.比较运算符 == != > < >= <= console.log(a <= b); console.log(a == b); console.log(a != b); console.log("=========="); //end //3.逻辑表达式 逻辑与(&&)和逻辑或(||) var ret = (a > 1) && (a < 2); console.log(ret); console.log(true && false); console.log("=========="); //end //4.字符串 a = 10; b = 20; var num_str = "" + a + b + true; console.log(num_str); //1020true num_str = a + b + true + ""; console.log(num_str); //31 console.log("=========="); //end //5.简约表达式 += -= *= /= ++ -- var c = null; a += c; //a = a + c a -= c; //a = a - c a *= c; //a = a * c a /= c; //a = a / c a = 10; a++; //a = a + 1 先参与运算，最后自增 ++a; //a = a + 1 先自增在参与运算 console.log(a); a--; //a = a - 1 先参与运算，最后自减 console.log(a); --a; //a = a - 1 先自减在参与运算 a = 4; console.log(a++); console.log(++a); // end