• JavaScript 运算符
• JavaScript 条件语句
• JavaScript 循环语句
• JavaScript 跳转语句

运算符

运算符.png

//任何类型与字符串相加都会默认转为字符串类型

<p> i = 10 ,j = 10 ,i+ j = ?</p>
    <p id="sumid"></p>
    <button onclick="mysum()">结果</button>
    <script>
        function mysum() {

            var i = 5;
            var j = ".3d";
            document.getElementById("sumid").innerHTML =i+j;
        }

var i = 11;
        document.write(i>10?"i大于10":"i小于10");

条件语句

1. if ...else

2. switch

<script>
        var i = 5;
        switch (i){
            case 1:
                document.write("i=1");
                break;
            case 2:
                document.write("i=2");
                break;
            default:
                document.write("条件不满足case")
            break;
        }
    </script>

循环语句

1.for 循环、for/in
2.while循环、do...while

var i =[1,2,3,4,5,6,7];

        for(var j = 0 ;j<i.length ; j++){
            document.write(i[j]+"、");
        }
        for(var j in  i){
            document.write(i[j]);
        }

<script>

        var i = 10;
        while (i< 10){

            document.write("i="+i+"<br/>");
            i++;
        }
        do{   do while先执行，后判断，一般用while即可

            document.write("i="+i+"<br/>");
            i++;
        }
        while (i< 10)


    </script>

JavaScript跳转语句

1.break 跳出循环
2.continue 跳出本次循环，进行下次循环