How to assign array into variable in jquery

The original and working array is this:

 var columns =[{
        name: 'level',
        minWidth: '200px'},
        {
        name: 'subject',
        minWidth: '70px'},
        {
        name: 'catid',
        minWidth: '70px'}],

However, I want to use if else statement to assign different array for different 'target' value. So I tried as below but it doesn't seem to supply the array correctly to the 'columns' variable.

 var useThis=[];
        if(target=="subject")
        {
            useThis = {
            name: 'level',
            minWidth: '200px'},
            {
            name: 'subject',
            minWidth: '70px'},
            {
            name: 'catid',
            minWidth: '70px'};

        }
        else
        {
            useThis = {
            name: 'level',
            minWidth: '200px'};

        }
var columns="["+useThis+"],";

How do I assign array correctly with if else statement?