Copy Specific Properties
22 August 2014
While working with some results from an API call, I needed to copy several (but not all) of their properties onto model objects I would use for application state. Most copy or clone functions grab every property from the source object but I wanted to just list a few.
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| function copy( prop ) { | |
| var receiver, target; | |
| function bindFrom( obj ) { | |
| target = obj; | |
| return copyProp(); | |
| } | |
| function bindTo( obj ) { | |
| receiver = obj; | |
| return copyProp(); | |
| } | |
| function copyProp() { | |
| if ( target && receiver ) { | |
| if ( prop in target ) { | |
| receiver[prop] = target[prop]; | |
| } | |
| return receiver; | |
| } | |
| return { | |
| from: bindFrom, | |
| to: bindTo | |
| }; | |
| } | |
| return copyProp(); | |
| }; |
I like code that tells a story. It’s hard for other developers (or future me) to get confused:
copy( 'some_property' ).from( objectA ).to( objectB );
When I use it to collect specific property values from API results, I map over a pre-determined list, like this:
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| var result = {id:1, foo: 'bar', baz: null}; | |
| var myObj = ['foo', 'baz'] | |
| .map( copy ) | |
| .reduce( function ( obj, copyProp ) { | |
| return copyProp.from( result ).to( obj ); | |
| }, {} ); | |
| //=> {foo: "bar", baz: null} |