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<meta charset="utf-8">
<title>javascript基础练习</title>
<style type="text/css">
body {text-align: center;}
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<script type="text/javascript">
document.write("换行的使用 <br/>,已经完成换行!");
alert("弹窗的使用\n,有换行的操作!,该弹窗尽量少用");
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<body>
<script src="text.js">外部引用的写法</script>
<input type="button" value="点击这里" onclick='alert("成功点击");'>
<br><br>
<p>JS的五种数据类型:undefined, number, string, boolean, object, function.</p>
<br><br>
<p style="color: red; font-size: 40px;">局部变量和全局变量</p>
<script type="text/javascript">
var a = 12;
function fun() {
var a = 23;
document.writeln(a);
}
document.writeln("fun()");
fun();
document.writeln(a);
var c = (a>=12)?15:0;
document.writeln(c);
console.log(typeof a);
</script>
<br><br>
<p>JS中算术运算符:+,-,*,/,%,++,--,-</p>
<p>比较运算符: >, <, >=, <=, ==, ===, !=, !==</p>
<p>逻辑运算符: !, &&, ||</p>
<br><br>
<P style="color: red; font-size: 40px;">写99乘法表</P>
<p style="text-align: left;">
<script type="text/javascript">
//var i = 1, j = 1;
for (var i = 1; i <= 9; i++) {
for (var j = 1; j <= i; j++)
{
document.writeln(i + '*' + j + '=' + (i*j) +' ');
}
document.writeln('<br/>')
}
</script>
</p>
<br><br>
<p style="color: red; font-size: 40px;">字符串转化为数字</p>
<script type="text/javascript">
var a = "657xxx";
var b = "78.89xxx";
var c = 123;
document.writeln('a' + '= ' + a + '<br/>');
document.writeln('b' + '= ' + b + '<br/>');
document.writeln('c' + '= ' + c + '<br/>');
document.writeln("parseInt(a)" + "=" + parseInt(a) + "<br/>");
document.writeln("parseInt(b)" + "=" + parseInt(b) + "<br/>");
document.writeln("parseInt(a)" + "=" + parseFloat(a) + "<br/>");
document.writeln("parseInt(b)" + "=" + parseFloat(b) + "<br/>");
document.writeln("isNaN(a)" + "=" + isNaN(a) + "<br/>");
document.writeln("isNaN(c)" + "=" + isNaN(c) + "<br/>");
</script>
<br><br>
<p style="color: red; font-size: 40px;">Math的使用</p>
<script type="text/javascript">
document.writeln("Math.random()" + "产生的随机数:" + Math.random() + "<br/>");
document.writeln("Math.random()" + "产生的随机数:" + Math.random() + "<br/>");
document.writeln("Math.max(12,13,-28)" + "最大值结果为:" + Math.max(12,13,-28) + "<br/>");
document.writeln("Math.pow(2,10)" + "2的10次方:" + Math.pow(2,10) + "<br/>");
</script>
<br><br>
<p style="color: red; font-size: 40px;">字符串的使用</p>
<script type="text/javascript">
var str = "Hello,kit,tom,jerry!";
document.write("str" + "=" + str + "<br/>");
document.writeln("str.length" + "=" + str.length + "<br>");
var array = str.split(",");
for (var i = array.length - 1; i >= 0; i--) {
document.writeln(array[i] + "<br/>");
}
for (var i = str.length; i > 0; i--) {
document.writeln(str.substring(0,i) + "<br/>");
}
</script>
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</body>
</html>
Js入门基础知识练习
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