2-JS运算符

1、运算符

1）算术运算符

 1 <button id="btn" onclick="suanShu()">运算</button>
 2 <script>
 3     // + - * / % ++ --
 4     var i = 521,j = 1314;
 5     var sum = i + j;
 6     var difference = j - i;
 7     var product = i * j;
 8     var quotient = j / i;
 9     var congruent = j % i;  //j除以i后的余数
10     var addSelf = i++;      // ++在前，先+后运算，++在后，先运算后加 此时i= 522
11     var selfCut = --j;      // --在前，先+后运算，--在后，先运算后加 此时j=1313
12     function suanShu() {
13         document.getElementById("sumId").innerHTML = "两数相加结果：" + sum;
14         document.getElementById("differenceId").innerHTML = "两数相减结果：" + difference;
15         document.getElementById("productId").innerHTML = "两数相乘结果：" + product;
16         document.getElementById("quotientId").innerHTML = "两数相除结果：" + quotient;
17         document.getElementById("congruentId").innerHTML = "两数取余结果：" + congruent;
18         document.getElementById("addSelfId").innerHTML = "i自加结果：" + addSelf;
19         document.getElementById("selfCutId").innerHTML = "j自减结果：" + selfCut;
20     }
21 </script>
22 <p id="sumId"></p>
23 <p id="differenceId"></p>
24 <p id="productId"></p>
25 <p id="quotientId"></p>
26 <p id="congruentId"></p>
27 <p id="addSelfId"></p>
28 <p id="selfCutId"></p>

2）赋值运算符

1 // = += -+ *= /= %=
2     var x = i+=j;       //i = i+j
3     var y = i -=j;      //i = i-j
4     var m = i *= j;     //i = i*j
5     var n = i /= j;      //i = i/j

3）字符串操作

字符串拼接：var i= 5+"5",结果为55.任何数据类型与字符串数据类型相加，都会转换为 字符串类型做处理

4）比较运算符 （== 、=== 、 != 、!==、>、<、>=、<= ）

 1 <script>
 2     var m = 12,n = "12";
 3     var x = 23,y = "23";
 4     document.write(m==n);   //true
 5     document.write(m===n);  //false
 6     document.write(m!=x);   //true
 7     document.write(m!==n);  //true
 8     document.write(m>y);    //false
 9     document.write(x<=n)    //false
10 </script>

5）逻辑运算符（&&、||、！）

1 <script>
2     var i = 100,j = 200;
3     document.write(i>100 && j<=200);    //与，两者都需满足
4     document.write(i>100 || j<=200);    //或，两者满足其一
5     document.write(!(i==j));    // 取反
6 </script>

6）条件运算符

<script>
    var i = 11;
    document.write(i>10 ? "i大于10":"i小于10"); //条件为真执行前，为假执行后
</script>