<script>
 var a="hello javascript"; 
 document.write("變量a的類型是:"+(typeof a));
 document.write("<br>");
 document.write("變量a的長度是:"+a.length);
</script>

<script>
 var a=10; 
 document.write("數(shù)字 "+a+" 轉(zhuǎn)換為字符串"+a.toString());
 document.write("<br>");

 var b=true; 
 document.write("布爾 "+b+" 轉(zhuǎn)換為字符串"+b.toString());
 document.write("<br>");

 var c="hello javascript"; 
 document.write("字符串 "+c+" 轉(zhuǎn)換為字符串 "+c.toString());
 document.write("<br>");

</script>

<script>
 var a=10; 
 document.write('默認(rèn)模式下，數(shù)字10轉(zhuǎn)換為十進(jìn)制的'+a.toString()); //默認(rèn)模式，即十進(jìn)制
 document.write("<br>"); 

 document.write('基模式下，數(shù)字10轉(zhuǎn)換為二進(jìn)制的'+a.toString(2)); //基模式，二進(jìn)制
 document.write("<br>"); 
 
 document.write('基模式下，數(shù)字10轉(zhuǎn)換為八進(jìn)制的'+a.toString(8)); //基模式，八進(jìn)制
 document.write("<br>"); 

 document.write('基模式下，數(shù)字10轉(zhuǎn)換為十六進(jìn)制的'+a.toString(16)); //基模式，十六進(jìn)制
 document.write("<br>"); 

</script>

<script>
 document.write("字符串的\"10\"轉(zhuǎn)換為數(shù)字的:"+parseInt("10")); //轉(zhuǎn)換整數(shù)
 document.write("<br>");
 document.write("字符串的\"3.14\"轉(zhuǎn)換為數(shù)字的:"+parseFloat("444 3.14"));//轉(zhuǎn)換浮點數(shù)
 document.write("<br>");
 document.write("字符串的\"10abc\"轉(zhuǎn)換為數(shù)字的:"+parseInt("10abc")); //判斷每一位，直到發(fā)現(xiàn)不是數(shù)字的那一位
 document.write("<br>");

 document.write("字符串的\"hello javascript\"轉(zhuǎn)換為數(shù)字的:"+parseInt("h5555ello javascript")); //如果完全不包含數(shù)字，則返

回NaN - Not a Number
 document.write("<br>");

</script>

<script>
 document.write("空字符串''轉(zhuǎn)換為布爾后的值:"+Boolean("")); //空字符串
 document.write("<br>");
 document.write("非空字符'hello javascript '串轉(zhuǎn)換為布爾后的值:"+Boolean("hello javascript")); //非空字符串
 document.write("<br>");
 document.write("數(shù)字 0 轉(zhuǎn)換為布爾后的值:"+Boolean(0)); //0
 document.write("<br>");
 document.write("數(shù)字 3.14 轉(zhuǎn)換為布爾后的值:"+Boolean(3.14)); //非0 
 document.write("<br>");
 document.write("空對象 null 轉(zhuǎn)換為布爾后的值:"+Boolean(null)); //null
 document.write("<br>");
 document.write("非對象 new Object() 轉(zhuǎn)換為布爾后的值:"+Boolean(new Object())); //對象存在
 document.write("<br>");
</script>

<script>
 document.write("通過Number() 函數(shù)轉(zhuǎn)換字符串'123' 后得到的數(shù)字："+Number("123"));  //正常的
 document.write("<br>");
 document.write("通過Number() 函數(shù)轉(zhuǎn)換字符串'123abc' 后得到的數(shù)字："+Number("123abc"));  //包含非數(shù)字
 document.write("<br>");
 document.write("通過Number() 函數(shù)轉(zhuǎn)換字符串'abc123' 后得到的數(shù)字："+Number("abc123"));  //包含非數(shù)字
 document.write("<br>");

 document.write("通過parseInt() 函數(shù)轉(zhuǎn)換字符串'123' 后得到的數(shù)字："+parseInt("123"));  //正常的
 document.write("<br>");
 document.write("通過parseInt() 函數(shù)轉(zhuǎn)換字符串'123abc' 后得到的數(shù)字："+parseInt("123abc"));  //包含非數(shù)字,返回開頭的合法

數(shù)字部分
 document.write("<br>");
 document.write("通過parseInt() 函數(shù)轉(zhuǎn)換字符串'abc123' 后得到的數(shù)字："+parseInt("abc123"));  //包含非數(shù)字,以非數(shù)字開頭，

返回NaN
 document.write("<br>");

</script>

<script>
 var a = null;
 document.write('String(null) 把空對象轉(zhuǎn)換為字符串：'+String(a)); 
 document.write("<br>"); 
 document.write('null.toString() 就會報錯，所以后面的代碼不能執(zhí)行'); 
 document.write(a.toString()); 
 document.write("因為第5行報錯，所以這一段文字不會顯示"); 
</script>