 <p>I think this should help you:-</p> <pre><code>var lols = [ { prop1: "h1", prop2: "h2", }, { prop1: "g1", prop2: "g2", } ] Object.keys(lols).map(function(key,index){ var lol = lols[key] lol["props3"]="g3" console.log(lol) }) </code></pre> <p>JS fiddle link <a href="https://jsfiddle.net/bps7zzf8/" rel="nofollow">https://jsfiddle.net/bps7zzf8/</a></p>