JavaScript work must Know (vi) Delete in instanceof

Inch

In determines whether the left -hand string or the property that can be converted to a string belongs to the right .

        var data = {x:1, y:4};//defines the direct object        alert ("x" in data),//true, X is a property of data        alert (1 in data),//false, 1 is the property value of data 。

　　

        var arr = [4, 5, 7];//defines the direct array object        alert (0 in arr);//true, the index of the ARR array includes 0,1,2,0 is one of his [0] properties.        alert (4 in arr);//false, 4 is not his attribute.

instanceof

instanceof you want the left instance to be the type of object on the right .

        var date = new Date ();        Alert (date instanceof date),//true        alert (date instanceof Object),//true        alert (date instanceof number);// False

　　

        var date = [1, 2, 3];        Alert (date instanceof Array),//true        alert (date instanceof Object),//true        alert (date instanceof number);// False    

　　

Delete

Delete Deletes an object's properties

        var o = {x:1, y:2};        Alert (delete o.x); True Delete Success        alert ("x" in O);//false x is not a property of O

         var o = 2;        Alert (delete this.o);//false        y = 3;        Alert (delete this.y);//true        alert (delete this.window);//false    

Summary

Delete is a unary operator, delete cannot delete global variables built into JavaScript, or global variables with var declarations, but you can delete global variables that are not declared with Var.

JavaScript work must Know (vi) Delete in instanceof