app.js

var array = ['a','b','c','d','e','f','g','h','i'];

var sort = function(array){
	var arrayA = [];
	var arrayB = [];

	var newArray = [];

	var half = Math.floor((array.length/2));

	for(var i=0;i<array.length;i++){
		if(i<=half){
			arrayA.push(array[i]);
		}else{
			arrayB.push(array[i]);
		}
	}

	for(var i=0;i<arrayA.length;i++){
		newArray.push(arrayA[i]);
		if(arrayB[i]){
			newArray.push(arrayB[i]);
		}
	}

	return newArray;
};

var printArray = function(array){
	for(var i=0;i<array.length;i=i+2){
		console.log(array[i],' ', array[i+1]?array[i+1]:'');
	}
};


printArray(sort(array));