Getting JavaScript object key list

Question

I have a JavaScript object like

var obj = {
   key1: \'value1\',
   key2: \'value2\',
   key3: \'value3\',
   key4: \'value4\'
}

How can I

Answer 1

var obj = {
   key1: 'value1',
   key2: 'value2',
   key3: 'value3',
   key4: 'value4'
};
var keys = [];

for (var k in obj) keys.push(k);

alert("total " + keys.length + " keys: " + keys);