Interesting JavaScript Array length problem Code Description _ javascript skills

Interesting JavaScript Array code example. For more information about js learning, see. Pay attention to the following situations. First:

The Code is as follows:

Var lennon = Array ();
Lennon ["name"] = "windy ";
Lennon ["year"] = "1989 ";
Lennon ["living"] = true;
Alert (lennon. length );

Result: lennon. length is 0.

Cause:
Add an array element without changing the length of the array.
Arr ["a"] = 3;
Second point:

The Code is as follows:

Var foo2 = [];
Foo2 ['3'] = 3;
Foo2 ['age'] = 20;
Debugger;
Alert (foo2.length );

Foo2.length is 4 again

All array objects without assignment will be defined as undefined.
JavaScript can automatically re-adjust the array size. This automatic size adjustment mechanism makes it easier to see out of bounds arrays and is more difficult to find out. Pay more attention to similar situations.