<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>运算符</title>
<script>
var num1 = 1;//赋值运算符,将右边的值赋给左边变量,则变量拥有值
var num2 = num1 + 1;//加法运算
/*
* 常用算数运算符
* + : 加 例:1+2=3
* - : 减 例:2-1=1
* * : 乘 例:2*3=6
* / : 除 例:6/2=3
* % : 求余 例:5%2=1;
* ++ : 自增 例:a++等于a+1;++a
* -- : 自减 例:a--等于a-1;--a
* a++与++a的区别:前者先运算后+1;后者先+1后运算
*
* 常用赋值运算符
* += : a+=b等同a=a+b;
* -= *= /= %=类同
*/
var str1 = "Hello";//"Hello"与"Hello "为不同字符串
var str2 = "World";//"World"与" World"为不同字符串
var str3 = str1+" "+str2;//字符串的相加为字符串的拼接
var str4 = str1 + num2;//字符串与数字的相加,结果为字符串,相当于把数字转换为字符串
</script>
</head>
<body>
<h2>结果查看</h2>
<p>
<script>
document.write("num1 = "+num1+"<br />"+"num2 = "+num2+"<br />");
document.write("str3 = "+str3+"<br />"+"str4 = "+str4);
</script>
</p>
</body>
</html>
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>运算符</title>
</head>
<body>
<h1>结果:</h1>
<script>
/*
* 比较运算符,返回布尔值True或者false,比较结果正确True,反正false
* == : 比较数值相等
* === : 全等(数值和类型)
* != : 不等于
* > : 大于
* < : 小于
* >= : 大于等于
* <= : 小于等于
*/
var num1 = 7;//赋值运算
if(num1 == 7){//比较变量值和数值
document.write("True");//比较结果,正确是返回
}else{
document.write("False");//比较结果错误是返回
}
document.write("<br />");
if(num1 === "7"){//数值和类型均符合才为真
document.write("True");
}else{
document.write("False");
}
/*
* 逻辑运算符,返回True或false True:1 false:0
* || : 或(一1则1)
* && : 与(一0则0)
* ! : 非(!1则0,!0则1)
*/
document.write("<br />"+"逻辑与结果:"+(true||false));
document.write("<br />"+"逻辑或结果:"+(true&&false));
document.write("<br />"+"逻辑非结果:"+(!0));
/*
* 条件运算符
* boole?aa:bb 如果ture则aa否则bb
*/
document.write("<br />"+"条件运算结果:"+(1>2 ? true : false));
/*
*
*/
</script>
</body>
</html>
- Boolean对象可以检查对象的逻辑结果(true/false)
- Boolean对象可以将非逻辑值转换为逻辑值
- 只有对象 无初始值,0,-0,null,"",false,undefined,NaN 返回false,其他返回true
- 注意:字符串'0',"false"值是true,只有空字符串为false.
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<style type="text/css">
.code{
color: gray;
border: 1px solid gainsboro;
font-size: 15px;
}
pre{
margin: 1em 0em 1em -19em;
font-family: "楷体";
}
.result{
color: gray;
background-color: ghostwhite;
font-size: 16px;
padding: 0.5em 1em;
}
h3{
color: red;
}
.result span:first-child{
display: block;
float: left;
width: 10em;
color: black;
}
</style>
<script type="text/javascript">
function objDisplay(eleId,obj){
if(typeof(eleId)!="string" || typeof(obj)!="object"){
alert("Function objDisplay() need the first parameter string and second object !")
}else{
var ele = document.getElementById(eleId);
if(!ele || !obj){
alert("Please check the parameter !")
}else{
for(i in obj){
var div = document.createElement("div");
for(var j=0;j<2;j++){
var span = document.createElement("span");
if(j==0) span.innerHTML = i+" : ";
else span.innerHTML = obj[i];
div.appendChild(span);
}
ele.appendChild(div);
}
}
}
}
</script>
</head>
<body>
<ul>
<li>
<h3>Boolean对象</h3>
<h4>代码:</h4>
<div class="code">
<pre>
//新建boolean对象
var booEty = new Boolean();
//布尔值
var booDict={
"Boolean()":new Boolean(),
"Boolean(0)":new Boolean(0),
"Boolean(-0)":new Boolean(-0),
"Boolean(null)":new Boolean(null),
"Boolean('')":new Boolean(''),
"Boolean(false)":new Boolean(false),
"Boolean(undefined)":new Boolean(undefined),
"Boolean(NaN)":new Boolean(NaN),
"Boolean('0')":new Boolean('0'),
"Boolean(1)":new Boolean(1),
"Boolean('false')":new Boolean('false')
}
objDisplay("dict01",booDict);
</pre>
</div>
<h4>结果:</h4>
<div id="dict01" class="result"></div>
<hr />
<script>
//新建boolean对象
var booEty = new Boolean();
//布尔值
var booDict={
"Boolean()":new Boolean(),
"Boolean(0)":new Boolean(0),
"Boolean(-0)":new Boolean(-0),
"Boolean(null)":new Boolean(null),
"Boolean('')":new Boolean(''),
"Boolean(false)":new Boolean(false),
"Boolean(undefined)":new Boolean(undefined),
"Boolean(NaN)":new Boolean(NaN),
"Boolean('0')":new Boolean('0'),
"Boolean(1)":new Boolean(1),
"Boolean('false')":new Boolean('false')
}
objDisplay("dict01",booDict);
</script>
</li>
</ul>
</body>
</html>
