JavaScript-js tutorial

This article mainly introduces the sharing of custom functions for JavaScript to determine whether a variable is null. This article provides the implementation code directly. For more information, see JavaScript, which does not determine whether a variable is null, the variables may be of the string, object, number, boolean, and Other types. The judgment methods vary depending on different types. So I wrote a function in the article to determine whether the JS variable is null. If it is undefined, null, '', NaN, false, 0, [], {}, blank string, true is returned; otherwise, false is returned.

The Code is as follows:

Function isEmpty (v ){
Switch (typeof v ){
Case 'undefined ':
Return true;
Case 'string ':
If (v. replace (/(^ [\ t \ n \ r] *) | ([\ t \ n \ r] * $)/g ,''). length = 0) return true;
Break;
Case 'boolean ':
If (! V) return true;
Break;
Case 'number ':
If (0 = v | isNaN (v) return true;
Break;
Case 'object ':
If (null = v | v. length = 0) return true;
For (var I in v ){
Return false;
}
Return true;
}
Return false;
}

Test:

The Code is as follows:

IsEmpty () // true
IsEmpty ([]) // true
IsEmpty ({}) // true
IsEmpty (0) // true
IsEmpty (Number ("abc") // true
IsEmpty ("") // true
IsEmpty ("") // true
IsEmpty (false) // true
IsEmpty (null) // true
IsEmpty (undefined) // true