var i = 10;

var a = i++;        // i = i + 1;

alert(a);

alert ( 10 > 5 );

var i = 100;

var n = 100;

alert(i == n);

alert(i != n);

alert(i === n) 

var i = 8;     //outputs false

alert ( i<5 && i<10);        //outputs true

alert(!(10 > 5));            //outputs false

if(condition) statements1 else statement2

if(10 > 5) {

        alert(“hello world”);

    }

    var i = 90;

    if(i > 100) {

        alert(i + “大于100”);

    }else if(i > 80) {

         alert(i + “大于80”);

    }else{

         alert(i + “小于100”);

    }

switch (expression){

        case value:

            //statement

            break;

        case value:

            //statement

            break;

        default:

            //statement

    }

 var i = 25;

    switch(i){

        case 25:

            alert(i + "等于 25");

            break;

        case 100:

            alert(100);

            break;

        default:

            alert(‘other’);

 }