Summary of data type conversion in JavaScript

In js, data type conversion is divided into explicit data type conversion and implicit data type conversion.

1, Explicit data type conversion

a: Convert to number:

1) Number conversion:

Code:

var a = “123”;
 
a = Number(a);

Note:

a) If the converted content itself is a numeric type string, it will return itself during future conversion.

b) If the content to be converted is not a numeric string, the result will be NaN.

c) If the content to be converted is an empty string, then The result of the conversion is 0.

d) If it is other characters, the result will be NaN.

2) parseInt():

code ：

var a = “123”; a = parseInt(a);

a) Ignore the spaces in front of the string until the first non-empty character is found, and the number after the number will also be Non-numeric strings are removed.

b) If the first character is not a numeric sign or a negative sign, NaN is returned

c) The decimal will be rounded. (Round down)

3) parseFloat();//Floating point number (decimal)

Same as parseInt, the only difference is that parseFloat can retain decimals.

b. Convert to string

You can convert other data types into strings.

1) String():

Code:

var a = 123;
 
a = String(a);

2) toString() method to convert ( packaging type).

Code:

var a = 123; a = a.toString();
 
undefined，null不能用toString。
   
c.转boolean类型：
可以将其它类型转为boolean值：
Boolean():
代码：
var a =”true”; a = Boolean(a);
注意：在进行boolean转换的时候所有的内容在转换以后结果都是true，除了：false、""（空字符串）、0、NaN、undefined
2，隐式转换
a) 转number:
var a = “123”;
a = +a;
加减乘除以及最余都可以让字符串隐式转换成number.
b) 转string:
var a = 123;
a = a + “”;
c) 转boolean:
var a = 123;
a = !!a;

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