Javascript basic tutorial data type conversion

JavaScript is an untyped language, but at the same time JavaScript provides a flexible method of automatic type conversion. The basic rule is that if a value of a certain type is used in a context that requires a value of another type, JavaScript will automatically convert the value to the required type.

All languages ​​have the ability to type conversion, and JavaScript is no exception. It also provides developers with a large number of type conversion access methods. Through global functions, more complex data types can be implemented.

var a = 3;
var b = a + 3;
var c = "student" + a;
var d = a.toString();
var e = a + "";
document.write(typeof(a) + " " + typeof (b) + " " +typeof (c) + " " + typeof (d) + " " + typeof (e));
//输出 number number string string string

The simplest example of type conversion

var a=b=c=d=e=4;
var f = a+b+c+d+ c.toString();
document.write(f);
// 输出  结果 164

For data type conversion to string, use toString() JavaScript to convert to string and implement mechanism conversion.

var a =111;
document.writeln(a.toString(2)+"");
document.writeln(a.toString(3)+"");
document.writeln(a.toString(8)+"");
document.writeln(a.toString(10)+"");
document.writeln(a.toString(16)+"");
//执行结果
//
1101111
11010
157
111
6f

Convert string to numeric type. JavaScript can use parseInt() and parseFloat() for conversion. Just like the name of the method, the former converts characters into integers and the latter converts characters into floating point numbers. . Only characters can be dispatched to these two methods, otherwise it is converted to NaN. No more operations are performed.

parseInt() first checks the character at subscript 0. If this character is a valid character, then checks the character at 1. If it is not a valid character, the conversion is terminated. The following example is an example of parseInt()

document.writeln(parseInt("4555.5544")+"");
document.writeln(parseInt("0.5544")+"");
document.writeln(parseInt("1221abes5544")+"");
document.writeln(parseInt("0xc")+"");//直接进行进制转化
document.writeln(parseInt("ahthw@hotmail.com")+"<br>");
//执行结果
4555
0
1221
12
NaN

Using parseInt, hexadecimal conversion can also be easily achieved. (parseFloat() is similar to parseFlaot, so no examples will be given here.)

document.writeln(parseInt("0421",8)+"");
document.writeln(parseInt("0421")+"");
document.writeln(parseInt("0421",16)+"");
document.writeln(parseInt("AF",16)+"");
document.writeln(parseInt("011",10)+"");
//输出结果
273
421
1057
175
11

The above is the entire content of this chapter. For more related tutorials, please visit JavaScript Video Tutorial!