CODEWITHSUNDEEP
javascriptjqueryarraysflatten
Alexander Dixon
Alexander Dixon

Reputation: 874

JavaScript split array in half juxtapose the first half with second half

What is the method to evenly split an array into two. Then, position the second half underneath the first all for the purpose of comparing whether or not a new final array should receive a zero or one in the slots.

var master_array = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38];

var first_half = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19];

var second_half = [20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38];

var final_usable_array_reduced = [];

So, given a form with 38 check boxes, if the 5th, 19th, 37th, and 38th check boxes were checked, the final_usable_array_reduced would be

final_usable_array_reduced = [0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1];

final_usable_array_reduced[4] = **represents the 5th <strong>or</strong> 24th box being checked**

final_usable_array_reduced[18] = **represents the 19th <strong>or</strong> 38th boxes being checked**

Upvotes: 0

Views: 547

Answers (3)

Twisty
Twisty

Reputation: 30893

Consider the following.

$(function() {
  function addChecks(count, tObj, cont) {
    var i;
    if (cont == undefined) {
      i = 0;
    } else {
      i = parseInt($("input:last").val()) - 1;
      count = i + count;
    }
    for (i; i <= count; i++) {
      $("<input>", {
        type: "checkbox",
        value: (i + 1),
        title: (i + 1)
      }).appendTo(tObj);
    }
  }

  function checksToArray() {
    var arr = [];
    $("input[type='checkbox']").each(function() {
      arr.push($(this).prop("checked"));
    });
    return arr;
  }

  function compHalfArr(a) {
    var arr = [];
    var h = Math.floor(a.length / 2);
    for (var i = 0; i <= h; i++) {
      arr.push(a[i] || a[(i + h)]);
    }
    return arr;
  }

  addChecks(14, $(".section-1"));
  addChecks(14, $(".section-2"), true);

  $("button").click(function() {
    var allChecks = checksToArray();
    var compChecks = compHalfArr(allChecks);
    $(".results").html("<span>" + compChecks.join("</span><span>") + "</span>").find("span:last").remove();
  });
});
.checks input {
  margin-right: 20px;
}

.results span {
  display: inline-block;
  font-family: Arial, sans-serif;
  width: 40px;
  text-align: center;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="checks section-1"></div>
<div class="checks section-2"></div>
<button>Check</button>
<div class="results"></div>

You can do a loop using a halfway marker.

Upvotes: 1

Macarthurval
Macarthurval

Reputation: 178

Check this one:

var array = [0,0,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0];
var firstHalf = array.slice(0,array.length/2);
var secondHalf = array.slice(array.length/2);
var result = firstHalf.map(function(e,i){
    return e || secondHalf[i];
});

console.log(result);

What I'm doing here is spliting the array into two halfs with slice (considering that the array elements are even, of course), and after that I map the first one returning 1 (or true, is the same) if firstArray[i] or secondArray[1] is 1.

Upvotes: 1

Nick
Nick

Reputation: 147166

I think you can implement this with a simple for loop over half the master_array, oring the values in the bottom half of the array with those in the top half:

var master_array = new Array(38).fill(0);
master_array[4] = 1;
master_array[18] = 1;
master_array[36] = 1;
master_array[37] = 1;

let len = master_array.length / 2;
final_usable_array_reduced = new Array(len);
for (let i = 0; i < len; i++) {
  final_usable_array_reduced[i] = master_array[i] | master_array[i + len];
}
console.log(final_usable_array_reduced);

Upvotes: 1

Related Questions