How do you clone an array of objects using underscore?

Question

#!/usr/bin/env node var _ = require('underscore'); var a = [{f: 1}, {f:5}, {f:10}]; var b = _.clone(a); b[1].f = 55; console.log(JSON.stringify(a)); 

This results in:

[{"f":1},{"f":55},{"f":10}] 

Clone does not appear to be working! So I RTFM, and see this:

http://underscorejs.org/#clone

Create a shallow-copied clone of the object. Any nested objects or arrays will be copied by reference, not duplicated.

So _.clone is pretty useless. Is there a way to actually copy the array of objects?

Answer 1

Well, there is a trick! If clone does not "clone" nested objects, you can force it to by explicitly cloning each object inside a map call! Like this:

#!/usr/bin/env node var _ = require('underscore'); var a = [{f: 1}, {f:5}, {f:10}]; var b = _.map(a, _.clone);       // <---- b[1].f = 55; console.log(JSON.stringify(a)); 

Prints:

[{"f":1},{"f":5},{"f":10}] 

Yay! a is unchanged! I can now edit b to my liking!