我要评论一、转换函数
1、parseint()
parseint()函数可以将任何类型的值转换为整数。
例如：
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="x-ua-compatible" content="ie=edge">
<title>转换函数</title>
<script>
// parseint()
var box="34";
alert(typeof parseint(box)); // number
</script>
</head>
<body>
</body>
</html>结果：
从上面的截图中可以看出：使用了parseint()函数以后，box变成了整数。
注意：
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="x-ua-compatible" content="ie=edge">
<title>转换函数</title>
<script>
// parseint()
/* var box="34";
alert(typeof parseint(box)); // number */
var box="34sf3435"; //parseint(box)=34
var box1="987.67";//parseint(box1)=987
var box2="rr567";//parseint(box2)=nan
alert("box的值："+parseint(box)+",box1的值:"+parseint(box1)+",box2的值:"+parseint(box2));
</script>
</head>
<body>
</body>
</html>结果：
2、parsefloat()
parsefloat()转换函数可以将字符串转换为浮点数。
例如：
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="x-ua-compatible" content="ie=edge">
<title>转换函数</title>
<script>
// parseint()
/* var box="34";
alert(typeof parseint(box)); // number */
/* var box="34sf3435"; //parseint(box)=34
var box1="987.67";//parseint(box1)=987
var box2="rr567";//parseint(box2)=nan
alert("box的值："+parseint(box)+",box1的值:"+parseint(box1)+",box2的值:"+parseint(box2)); */
// parsefloat()
var box="12.345";
var box1=parsefloat(box);
alert(typeof box1);//number
</script>
</head>
<body>
</body>
</html>结果：
注意：
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="x-ua-compatible" content="ie=edge">
<title>转换函数</title>
<script>
// parseint()
/* var box="34";
alert(typeof parseint(box)); // number */
/* var box="34sf3435"; //parseint(box)=34
var box1="987.67";//parseint(box1)=987
var box2="rr567";//parseint(box2)=nan
alert("box的值："+parseint(box)+",box1的值:"+parseint(box1)+",box2的值:"+parseint(box2)); */
// parsefloat()
/* var box="12.345";
var box1=parsefloat(box);
alert(typeof box1);//number */
var box="34.435"; //parsefloat(box)=34
var box1="987.67ererw";//parsefloat(box1)=987.67
var box2="rr567.12";//parsefloat(box2)=nan
var box3="567wew.12";//parsefloat(box2)=nan
alert("box的值："+parsefloat(box)+",box1的值:"+parsefloat(box1)+",box2的值:"+parsefloat(box2)+",box3的值:"+parsefloat(box3));
</script>
</head>
<body>
</body>
</html>结果：
3、tostring()
tostring()转换函数返回字符串。
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="x-ua-compatible" content="ie=edge">
<title>转换函数</title>
<script>
// parseint()
/* var box="34";
alert(typeof parseint(box)); // number */
/* var box="34sf3435"; //parseint(box)=34
var box1="987.67";//parseint(box1)=987
var box2="rr567";//parseint(box2)=nan
alert("box的值："+parseint(box)+",box1的值:"+parseint(box1)+",box2的值:"+parseint(box2)); */
// parsefloat()
/* var box="12.345";
var box1=parsefloat(box);
alert(typeof box1);//number */
/* var box="34.435"; //parsefloat(box)=34
var box1="987.67ererw";//parsefloat(box1)=987.67
var box2="rr567.12";//parsefloat(box2)=nan
var box3="567wew.12";//parsefloat(box2)=nan
alert("box的值："+parsefloat(box)+",box1的值:"+parsefloat(box1)+",box2的值:"+parsefloat(box2)+",box3的值:"+parsefloat(box3)); */
// tostring()
var a=4;
var b=7;
alert(a.tostring()+b.tostring());// 输出47，不是11
</script>
</head>
<body>
</body>
</html>结果：
二、强制类型转换函数
1、boolean()
boolean()转换为boolean值。
例如：
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="x-ua-compatible" content="ie=edge">
<title>转换函数</title>
<script>
// parseint()
/* var box="34";
alert(typeof parseint(box)); // number */
/* var box="34sf3435"; //parseint(box)=34
var box1="987.67";//parseint(box1)=987
var box2="rr567";//parseint(box2)=nan
alert("box的值："+parseint(box)+",box1的值:"+parseint(box1)+",box2的值:"+parseint(box2)); */
// parsefloat()
/* var box="12.345";
var box1=parsefloat(box);
alert(typeof box1);//number */
/* var box="34.435"; //parsefloat(box)=34
var box1="987.67ererw";//parsefloat(box1)=987.67
var box2="rr567.12";//parsefloat(box2)=nan
var box3="567wew.12";//parsefloat(box2)=nan
alert("box的值："+parsefloat(box)+",box1的值:"+parsefloat(box1)+",box2的值:"+parsefloat(box2)+",box3的值:"+parsefloat(box3)); */
// tostring()
/* var a=4;
var b=7;
alert(a.tostring()+b.tostring());// 输出47，不是11 */
// boolean()
var a=8; //boolean(a)：true 任何非0的数字都是true
var b=0; //boolean(b)：false
var c="232"; // boolean(c)：true 任何非空的字符串都是true
var d="";// boolean(d)：false
var e; // boolean(e)：false
var f=null; //boolean(f)：false
document.write("a:"+boolean(a)+"<br />");
document.write("b:"+boolean(b)+"<br />");
document.write("c:"+boolean(c)+"<br />");
document.write("d:"+boolean(d)+"<br />");
document.write("e:"+boolean(e)+"<br />");
document.write("f:"+boolean(f)+"<br />");
</script>
</head>
<body>
</body>
</html>结果：
2、number()
number()转换为数字。
例如：
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="x-ua-compatible" content="ie=edge">
<title>转换函数</title>
<script>
// parseint()
/* var box="34";
alert(typeof parseint(box)); // number */
/* var box="34sf3435"; //parseint(box)=34
var box1="987.67";//parseint(box1)=987
var box2="rr567";//parseint(box2)=nan
alert("box的值："+parseint(box)+",box1的值:"+parseint(box1)+",box2的值:"+parseint(box2)); */
// parsefloat()
/* var box="12.345";
var box1=parsefloat(box);
alert(typeof box1);//number */
/* var box="34.435"; //parsefloat(box)=34
var box1="987.67ererw";//parsefloat(box1)=987.67
var box2="rr567.12";//parsefloat(box2)=nan
var box3="567wew.12";//parsefloat(box2)=nan
alert("box的值："+parsefloat(box)+",box1的值:"+parsefloat(box1)+",box2的值:"+parsefloat(box2)+",box3的值:"+parsefloat(box3)); */
// tostring()
/* var a=4;
var b=7;
alert(a.tostring()+b.tostring());// 输出47，不是11 */
// boolean()
/* var a=8; //boolean(a)：true 任何非0的数字都是true
var b=0; //boolean(b)：false
var c="232"; // boolean(c)：true 任何非空的字符串都是true
var d="";// boolean(d)：false
var e; // boolean(e)：false
var f=null; //boolean(f)：false
document.write("a:"+boolean(a)+"<br />");
document.write("b:"+boolean(b)+"<br />");
document.write("c:"+boolean(c)+"<br />");
document.write("d:"+boolean(d)+"<br />");
document.write("e:"+boolean(e)+"<br />");
document.write("f:"+boolean(f)+"<br />"); */
// number()
var a="34"; //number(a)：34
var b="67.34";//number(b)：67.34
var c="45ttt";//number(c)：nan
var d="";//number(d)：0
var e=true;//number(a)：1
var f=false;//number(a)：0
var g;//number(a)：nan
var h=null;//number(a)：0
document.write("a:"+number(a)+"<br />");
document.write("b:"+number(b)+"<br />");
document.write("c:"+number(c)+"<br />");
document.write("d:"+number(d)+"<br />");
document.write("e:"+number(e)+"<br />");
document.write("f:"+number(f)+"<br />");
document.write("g:"+number(g)+"<br />");
document.write("h:"+number(h)+"<br />");
</script>
</head>
<body>
</body>
</html>结果：
3、string()
string()转换为字符串。
例如：
<!doctype html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="x-ua-compatible" content="ie=edge">
<title>转换函数</title>
<script>
// parseint()
/* var box="34";
alert(typeof parseint(box)); // number */
/* var box="34sf3435"; //parseint(box)=34
var box1="987.67";//parseint(box1)=987
var box2="rr567";//parseint(box2)=nan
alert("box的值："+parseint(box)+",box1的值:"+parseint(box1)+",box2的值:"+parseint(box2)); */
// parsefloat()
/* var box="12.345";
var box1=parsefloat(box);
alert(typeof box1);//number */
/* var box="34.435"; //parsefloat(box)=34
var box1="987.67ererw";//parsefloat(box1)=987.67
var box2="rr567.12";//parsefloat(box2)=nan
var box3="567wew.12";//parsefloat(box2)=nan
alert("box的值："+parsefloat(box)+",box1的值:"+parsefloat(box1)+",box2的值:"+parsefloat(box2)+",box3的值:"+parsefloat(box3)); */
// tostring()
/* var a=4;
var b=7;
alert(a.tostring()+b.tostring());// 输出47，不是11 */
// boolean()
/* var a=8; //boolean(a)：true 任何非0的数字都是true
var b=0; //boolean(b)：false
var c="232"; // boolean(c)：true 任何非空的字符串都是true
var d="";// boolean(d)：false
var e; // boolean(e)：false
var f=null; //boolean(f)：false
document.write("a:"+boolean(a)+"<br />");
document.write("b:"+boolean(b)+"<br />");
document.write("c:"+boolean(c)+"<br />");
document.write("d:"+boolean(d)+"<br />");
document.write("e:"+boolean(e)+"<br />");
document.write("f:"+boolean(f)+"<br />"); */
// number()
/* var a="34"; //number(a)：34
var b="67.34";//number(b)：67.34
var c="45ttt";//number(c)：nan
var d="";//number(d)：0
var e=true;//number(e)：1
var f=false;//number(f)：0
var g;//number(g)：nan
var h=null;//number(h)：0
document.write("a:"+number(a)+"<br />");
document.write("b:"+number(b)+"<br />");
document.write("c:"+number(c)+"<br />");
document.write("d:"+number(d)+"<br />");
document.write("e:"+number(e)+"<br />");
document.write("f:"+number(f)+"<br />");
document.write("g:"+number(g)+"<br />");
document.write("h:"+number(h)+"<br />"); */
// string()
var a=34; //string(a)：34
var b=67.34;//string(b)：67.34
var c=true;//string(c)：true
var d=false;//string(d)：false
var e=null;//string(e)：null
var f; //string(f):undefined
document.write("a:"+string(a)+"<br />");
document.write("b:"+string(b)+"<br />");
document.write("c:"+string(c)+"<br />");
document.write("d:"+string(d)+"<br />");
document.write("e:"+string(e)+"<br />");
document.write("f:"+string(f)+"<br />");
</script>
</head>
<body>
</body>
</html>结果：
到此这篇关于javascript数据类型转换的文章就介绍到这了。希望对大家的学习有所帮助，也希望大家多多支持代码网。
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