JS Learning (i)

In JavaScript , what values can be used as the if condition?

1. boolean variable true/false

2. Digital

A value other than 0 is true, and 0 or NaN is false.

3. objects

object is null or undefined is false

4. string

The empty string ("" ) is false, and ("") This is true.

In summary, for a string, do not write a large heap if (str!=null && str!=undefined && str! = "), as long as a sentence

if (str) {

Do something

} It will be all right.

Javascript type conversion function

Isfinite (number) detects whether a value can be a finite digit, which returns TRUE or False
IsNaN (String) detects whether a value is not a finite number, not a digit, returns TRUE or False
Number () Converts the value of an object to a digit
parsefloat (String) resolves a string to a superficial number
parseint (String) parses a string into an integer, not four-in-five, but a cut-tail
String (object) converts an object value to a string