. 1 <! DOCTYPE HTML> 2 <HTML> . 3 <head> . 4 <Meta charset = "UTF-. 8"> . 5 <title> </ title> . 6 </ head> . 7 <body> . 8 <-! JavaScript basic data type . 9 typeof function to get the type of a variable; 10 Boolean : if the variable is a Boolean type . 11 Number: Number If the variable is type (integer, floating point) 12 is String: if the variable of type String (a " ',' ') 13 is Object: If the variable is a reference type or Null type 14 , such as: new new the Array () / new new String () ... 15 function : Function Type 16 undefined: if the variable is type Undefined -> . 17 <Script> 18 is var B = to true ; . 19 var B = 33 is ; 20 is var A = 'ABC' ; 21 is var A = "ABC" ; 22 is var Aa = 'the I Love "BIA BIA"' ; 23 is var obj = {name: 'zhangsan', Sex: 18 is }; 24 var List = [1,2,3,4 ]; 25 var OBJ1 = null ; 26 is Alert ( typeof(B)); 27 // print the results to the console 28 the console.log ( typeof (B)); 29 the console.log (A, typeof (A)); 30 the console.log (Aa); 31 is the console.log (obj, typeof (obj)); 32 the console.log (List, typeof (List)); 33 is the console.log (OBJ1, typeof (OBJ1)); 34 is </ Script> 35 ! <- the JavaScript data converter 36 Number The (): turn a strong value (including integer and floating point) 37 *parseInt (): Strong to Integer 38 is * parseFloat (): Strong float switch 39 Boolean (): boolean value into strong (only the empty string, null (null belong to the object), Number type 0, NaN only for the type of to false) 40 isNaN (): detecting whether a number is not NaN: not a number (Note: if the number of returns false, the number of type string also returns ture) -> 41 is <Script> 42 is // Note: contain any string when a non-numeric character represented by 43 is // Number the () returns NaN3 44 is // the parseInt () and parseFloat () returns a value of 45 46 is var STR = '1a123'; // character 47 var Number = RES (STR); // turn a Number 48 var res1 = parseInt(str); 49 var res2 = parseFloat(str); 50 console.log(res,typeof(res)); 51 console.log(res1,typeof(res1)); 52 console.log(res2,typeof(res2)); 53 console.log(str,isNaN(str)); 54 </script> 55 </body> 56 </html>