Array Init vs Array.push

array.js

/*
  Adding values in array at init using variables is faster
  then processing individual entity
*/
function A(options){
   var a = [ “something” + options.A + “more”,  “second elem” + options.B + “Yo!”]
   return A;
}
function B(options){
   var a = [];
   a.push( “something” + options.A + “more”);
   a.push(“second elem” + options.B + “Yo!”);
   return A;
}

For a set of 100000 calls on nodejs-v12 stats are

Function A: 6 ~ 8ms
Function B: 11 ~ 15ms

Explanation is quite simple Function invocation costs the engine to jump context, but JS Engine does optimise push calls by inlining them, still the inlined function also has to flatten the arguments and then push back the length property on the return stack of the context.