算术运算符包括:+ - * / % var++ ++var var-- --var

(1)+ - * / %

window.onload = function () {
  var a, b;
  a = 1, b = 2;
  console.log(a + b);
  console.log(a - b);
  console.log(a * b);
  console.log(a / b);
  console.log(a % b);
  document.write(a + b + '<br>');
  document.write(a * b);
}

控制台:

202103171615963701174378
页面:

202103171615963768157129

(2)var++后加

var a, b;
a = 1, b = 2;
var c = 5;
// c++参与过运算再加1,所以r=8,c++运算之后c=6,r+c=14
var r = a + b + c++;
console.log(r);
console.log(c);
console.log(r + c);

控制台:

202103171615963887911081

++var前加

var a, b;
a = 1, b = 2;
var d = 6;
// ++d先运算自身,再进行计算,所以z=10,d=7;
var z = a + b + (++d);
console.log(z);
console.log(d);

控制台:

202103171615964038496238

(3)var–后减

var a, b;
a = 1, b = 2;
var w = 10;
// w--参与过运算再加减,所以x=13,w--运算之后w=9 
var x = a + b + w--;
console.log(x);
console.log(w);

控制台:

202103171615964180307167

–var前减

var a, b;
a = 1, b = 2;
var f = 4;
// --y先运算自身,再进行计算,所以y=5,f=3; 
var y = a * b + (--f);
console.log(y);
console.log(f);

控制台:

202103171615964285128791