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villadora/propertyIsEnumerable.md

Created July 13, 2012 02:17
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propertyIsEnumerable & hasOwnProperty
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propertyIsEnumerable.md

hasOwnProperty

propertyIsEnumerable

哪些属性会在for... in ...中遍历， 哪些不会，可以通过propertyIsEnumerable进行测试

var a = ['is enumerable'];  
a.propertyIsEnumerable(0);          // returns true  
// 在javascript中array的也是通过hash map实现只不过index换成了number，所以0在这里也是enumerable的属性就可以理解了
a.propertyIsEnumerable('length');   // returns false  

Math.propertyIsEnumerable('random');   // returns false  
this.propertyIsEnumerable('Math');     // returns false
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