javascript - defining field in z={ field : 'value'} using variable? -

var = 'this'; 

i want

var z = { a: 'that' } === { 'this': 'that'} 

where as:-

alert( z.this); // output 'undefined'  alert(z.a); // output 'that'  

how define z's field using variable?

so that...

alert( z.this); // output becomes 'that' 

use case: dynamically create object z, instead of hardcoding fields.

in codee there no property this object z why alert(z.this) shows shows undefined. must not use property name reserved key word.

i think need define

var = 'this'; z[a]="that"; alert( z[a]); // output 'that'