i should make a jslib named bullshitjs

bullshit.js

var inputArray = [10, 20, 30, 42];

var addedArray = [];

inputArray.map(function(val,index){
  var thisIndex = index;
  if(thisIndex >= 1) {
    var prevIndex = thisIndex-1;
  }
  addedArray.push(inputArray[thisIndex] + inputArray[prevIndex])
  
});