JQuery_2.1.0_日記 5.1

JQuery工具方法.

(1)$.isNumeric(obj)

    此方法判斷傳入的對象是否是一個數字或者可以轉換爲數字.

    isNumeric: function( obj ) {

        // parseFloat NaNs numeric-cast false positives (null|true|false|"")

       // ...but misinterprets leading-number strings, particularly hex literals ("0x...")

       // subtraction forces infinities to NaN

       return obj - parseFloat( obj ) >= 0;

  },

用'-'號先將obj轉換爲數字，這麼做是因爲如果傳入的字符串中含有非數字字符,那麼obj將被轉換爲NaN,isNumeric將返回false.

alert( '55a'-0) //NaN

注意：js的原生方法parseFloat在處理16進制字符串時會出現轉換錯誤,他會取16進制的標誌0x的0.....

var f = parseFloat('0xAAAA' , 2);

alert(f); //0

Test_Script

var obj = {toString: function(){

     return '6' ;

}};

var f = $.isNumeric(obj);

alert(f);//true

(2)isPlainObject(obj)

此方法判斷傳入的對象是否是'純淨'的對象,即使用字面量{},或new Object()創建的對象.

Test_Script

function Person(name, age) {

    this .name = name;

    this .age = age;

};

              

 var p = $.isPlainObject( new Person());

              

alert(p); //false

              

alert($.isPlainObject({})); //true

              

alert($.isPlainObject(document.getElementById( 'div1'))); //false

isPlainObject(obj)源碼

isPlainObject: function( obj ) {

               //不是object或者是DOM元素或是window返回false

               if ( jQuery.type( obj ) !== "object" || obj.nodeType || jQuery.isWindow( obj ) ) {

                      return false ;

              }

               // Support: Firefox <20

               // The try/catch suppresses exceptions thrown when attempting to access

               // the "constructor" property of certain host objects, ie. |window.location|

               // https://bugzilla.mozilla.org/show_bug.cgi?id=814622

               try {

                      //是自定義對象返回false

                      //判斷自定義對象的依據是如果isPrototypeOf方法是從{}的原型對象中繼承來的那麼便是自定義對象

                      if ( obj.constructor &&

                                  !hasOwn.call( obj.constructor.prototype, "isPrototypeOf" ) ) {

                            return false ;

                     }

              } catch ( e ) {

                      return false ;

              }

               // If the function hasn't returned already, we're confident that

               // |obj | is a plain object, created by {} or constructed with new Object

               return true ;

       },