how to make a deep copy in javascript

1JSON.parse(JSON.stringify(o))

1function copy(arr1, arr2) {
2	for (var i =0; i< arr1.length; i++) {
3    	arr2[i] = arr1[i];
4    }
5}
6copy(arr1, arr2)

1//recursive deep copy of object
2function dup(o) {
3    // "string", number, boolean
4    if(typeof(o) != "object") {
5        return o;
6    }
7    
8     // null
9    if(!o) {
10        return o; // null
11    }
12    
13    var r = (o instanceof Array) ? [] : {};
14    for(var i in o) {
15        if(o.hasOwnProperty(i)) {
16            r[i] = dup(o[i]);
17        }
18    }
19    return r;
20}
21