1 : Pseudo- Object 2 : Convert to String 3 : Numeric to String 4 : Convert to Digital 5 : Convert to Boolean 6 : The difference between number () and parseint () 7 : The difference between String () and ToString ()
Pseudo-Object concepts: JavaScript is a very interesting language, and even basic types are pseudo-objects, so they all have properties and methods. The type of variable A is a string that gets its length by calling its property length as a pseudo-object
<script>
var a= "Hello JavaScript";
document.write ("Variable A is of type:" + (typeof a));
document.write ("<br>");
document.write ("The length of variable A is:" +a.length);
</script>
either Number,boolean or string has a ToString method that is used to convert to a string<script>varA=Ten; document.write ("Digital"-am"Convert to String"+a.tostring ()); document.write ("<br>"); varb=true; document.write ("Boolean"+b+"Convert to String"+b.tostring ()); document.write ("<br>"); varC="Hello JavaScript"; document.write ("string"+c+"Convert to String"+c.tostring ()); document.write ("<br>"); </script>
when number is converted to a string, there are both default mode and base mode.<script>varA=Ten; document.write ('In default mode, the number 10 is converted to decimal'+a.tostring ());//default mode, which is the decimaldocument.write ("<br>"); document.write ('In base mode, the number 10 is converted to binary'+a.tostring (2));//base mode, binarydocument.write ("<br>"); document.write ('In base mode, the number 10 is converted to octal'+a.tostring (8));//base mode, octaldocument.write ("<br>"); document.write ('base mode, the number 10 is converted to 16 binary'+a.tostring ( -));//base mode, Hexdocument.write ("<br>"); </script>
JavaScript provides built-in functions parseint () and parsefloat (), respectively, to digital note: If the string being converted, along with numbers and characters, the parseint will always position the number until non-characters appear. So"10ABC"will be converted toTen<script>document.write ("The \ "10\" of the string is converted to a number:"+parseint ("Ten"));//converting integersdocument.write ("<br>"); document.write ("The \ "3.14\" of the string is converted to a number:"+parsefloat ("3.14"));//convert floating-point numbersdocument.write ("<br>"); document.write ("The \ "10abc\" of the string is converted to a number:"+parseint ("10ABC"));//judge every bit until you find the one that is not the numberdocument.write ("<br>"); document.write ("The \ "Hello javascript\" of the string is converted to a number:"+parseint ("Hello JavaScript"));//returns nan-not a number if it does not contain numbers at alldocument.write ("<br>"); </script>
when using the built-in function Boolean () to convert a string to a Boolean worth: Non-NULL is true when converting a number: Not 0 is true when converting an object: Non-null is true<script>document.write ("An empty string ' is converted to a Boolean value:"+boolean (""));//empty stringdocument.write ("<br>"); document.write ("the non-null character ' Hello JavaScript ' string is converted to a Boolean value:"+boolean ("Hello JavaScript"));//non-empty stringdocument.write ("<br>"); document.write ("the number 0 is converted to a Boolean value:"+boolean (0));//0document.write ("<br>"); document.write ("the number 3.14 is converted to a Boolean value:"+boolean (3.14));//not 0document.write ("<br>"); document.write ("empty object null is converted to a Boolean value:"+boolean (NULL));//NULLdocument.write ("<br>"); document.write ("non-Object new object () is converted to a Boolean value:"+boolean (NewObject ()));//Object existsdocument.write ("<br>"); </script>
number (), like parseint (), can be used to make a numeric conversion difference in that when the content of the conversion contains non-numbers, number () will return Nan (not a number) parseint () depends on the situation, if the numbers start with, Returns a valid number part at the beginning, or Nan if it starts with a non-digit<script>document.write ("the number that is obtained after the string ' 123 ' is converted through the # () function:"+number ("123"));//Normal.document.write ("<br>"); document.write ("the number that is obtained after the string ' 123abc ' is converted by the # () function:"+number ("123ABC"));//contains non-numericdocument.write ("<br>"); document.write ("the number that is obtained after the string ' abc123 ' is converted through the # () function:"+number ("abc123"));//contains non-numericdocument.write ("<br>"); document.write ("the number obtained after converting the string ' 123 ' through the parseint () function:"+parseint ("123"));//Normal.document.write ("<br>"); document.write ("the number obtained after converting the string ' 123abc ' by the parseint () function:"+parseint ("123ABC"));//contains non-numeric, returns the legal number part at the beginningdocument.write ("<br>"); document.write ("the number that is obtained after the string ' abc123 ' is converted by the parseint () function:"+parseint ("abc123"));//contains non-numeric, starts with a non-digit, returns Nandocument.write ("<br>"); </script>
String ( ) and ToString () will return strings, except that a string () that handles NULL is returned ."NULL"toString () will error and cannot be executed<script>varA =NULL; document.write ('string (NULL) to convert an empty object to a string:'+String (a)); document.write ("<br>"); document.write ('null.tostring () will error, so the subsequent code cannot be executed'); document.write (A.tostring ()); document.write ("because the 5th line error, so this paragraph of text will not show"); </script>
JAVASCRIPT type Conversion