MultiDArrayFlatten.js

// Flatten Multi Dimensional Array
var multiDArray = [[1, 2], [3], [4, 5]];
var flatArray = [];
console.log(multiDArray);
for (var i = 0; i < multiDArray.length; i++) {
  for (var j = 0; j < multiDArray[i].length; j++) {
    flatArray.push(multiDArray[i][j]);
  }
}
console.log(flatArray);