JS data type and type conversion

(1) display conversion type:

1.Number (a) is used to convert object a as a whole.

var a= ' 12345 ';

Number (a); a=12345

2.parseInt (a) is used to convert an object a from front to back, to start with a non-numeric stop conversion, to convert to an integer.

var a= ' 100px ';

parseint (a); a=100;

var a= ' +100px ';

parseint (a); a=100 for some of the ' +,-, Space ' symbols can be identified

3.parseFloat (a,10) is used to convert object a from post to decimal ; ' denotes decimal.

var a= ' 12.34 yuan ';

Parsefloat (a); a=12.34;

var a= ' 12.34.12 yuan ';

Parsefloat (a);     a=12.34; only one decimal points can be identified

(2) implicit conversion type:

1.+ (200+'1') converted to a string

2.-*/% ('3') converted to digital

3.++--(a= '; a++ ') converted into numbers

Comparison of 4.> < numbers is different from string comparison

Alert (' >9 '); True

Alert (' Ten ' > ' 9 '); False

5.! Inverse (converts the right data type to a Boolean value)

6. = = value comparison; = = = The comparison of the advanced types, then the comparison of the values

Alert (' 2 ' ==2); True

7.isNaN used to determine whether the number is the number returned false , not a numeric return true

(Working principle: First Use the number () method to convert, and then judge)

IsNaN (' 250 '); False

JS data type and type conversion