一:js的數據類型
1:基本數據類型:number string boolean null undefined
2:複雜數據類型:Array Function Objeck Data Math RegExp(正則表達式) Number String Boolean
二:檢測的方法
1:數據類型
typeof :檢測所有的基本數據類型的方法,除null 之外,還有function
用法:typeof(需要檢測的數據類型)
2檢測數組
第一種:isArray()
var arr = [ 10 , 20 , 30 ] ;
console. log ( Array. isArray ( arr) ) ;
第二種:instanceof :用來檢測數組不是很嚴謹
var arr1 = [ 10 , 20 , 30 ] ;
console. log ( arr1 instanceof Array ) ;
第三種 toString();
用法:Object.prototype.toString.call(需要檢測的數據類型)
console. log ( Object. prototype. toString. call ( 1 ) ) ;
console. log ( Object. prototype. toString. call ( 'a' ) ) ;
console. log ( Object. prototype. toString. call ( true ) ) ;
console. log ( Object. prototype. toString. call ( undefined) ) ;
console. log ( Object. prototype. toString. call ( null ) ) ;
console. log ( Object. prototype. toString. call ( [ 1 , 2 , 3 ] ) ) ;
console. log ( Object. prototype. toString. call ( new Object ( ) ) ;
console. log ( Object. prototype. toString. call ( function ( ) { } ) ;
三 :關於null not is anumber(不是一個數字)
isNaN ( ) ; 用來判斷一個數值是否是數字.
console. log ( isNaN ( 100 ) ) ;
console. log ( isNaN ( 'abc' ) ) ;
console. log ( isNaN ( '100' ) ) ;
四:基本包裝類型–>Number
var num = new Number ( 123 ) ;
console. log ( num) ;
console. log ( num. toString ( ) ) ;
console. log ( num. valueOf ( ) ) ;
五:Boolean
var b1 = true ;
b1. toString ( ) ;