Get number of non-empty elements from nested arrays

Question

I have ten arrays with empty value

onTable[0 to 10];

look

["Jean5", "Jean3", "Paul2", "Jean6", "", "Paul4", "Jean", "peirre4", ""]
["Paul5", "peirre6", "peirre3", "", "Jean4", "Paul", "peirre5", "Jean2", ""]
...

I want get length of each array without empty value and without create ten variables for check that.

I have test this solution count empty values in array but i dont want make ten variable. ie: count1, count2,....

I check too compare two arrays based on length: skip empty values but is not what i want.

If possible, I want this look like

onTable[0].length(exclude(""))

What is the good way for make that?

filter will not update the existing array.... it's just return the new array — Pranav C Balan, Nov 19 '15 at 11:42

Tushar · Accepted Answer · 2015-11-19T11:43:09.513

Use filter with Boolean to filter non-empty elements from sub-array and use length on it.

onTable[0].filter(Boolean).length

As empty string is falsy in JavaScript, it'll be removed from filtered array.

Demo:

var arr = [
  ["Jean5", "Jean3", "Paul2", "Jean6", "", "Paul4", "Jean", "peirre4", ""],
  ["Paul5", "peirre6", "peirre3", "", "Jean4", "Paul", "peirre5", "Jean2", ""]
];

var len = arr[1].filter(Boolean).length;
document.write(len);

score 1 · Answer 2 · answered Nov 19 '15 at 11:53

You can use filter function for your need: check value to undefined or null etc.

var arr = [
  ["Jean5", "Jean3", "Paul2", "Jean6", "", "Paul4", "Jean", "peirre4", ""],
  ["Paul5", "peirre6", "peirre3", "", "Jean4", "Paul", "peirre5", "Jean2", ""]
];

var len = arr[1].filter(function(x){ return x != ""}).length;
document.write(len);

score 1 · Answer 3 · answered Nov 19 '15 at 11:53

With a prototype:

Array.prototype.lengthWihtoutEmptyValues = function () {
    var initialLength = this.length;
    var finalLength = initialLength;

    for (var i = 0; i < initialLength; i++) {
        if (this[i] == "") {
            finalLength--;
        }
    }

    return finalLength;
}

var arrays = [
  ["Jean5", "Jean3", "Paul2", "Jean6", "", "Paul4", "Jean", "peirre4", ""],
  ["Paul5", "peirre6", "peirre3", "", "Jean4", "Paul", "peirre5", "Jean2", ""]
];

var arrayLength = arrays[0].lengthWihtoutEmptyValues();

$("#arrayLength").html(arrayLength);

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="arrayLength"></div>

score 0 · Answer 4 · answered Nov 23 '15 at 06:49

You should avoid "wasting" memory and inducing excessive GC. You can reduce() each sub array to a count of it's non-empty values:

sub.reduce(function(prev, cur) {
  return prev + (!!cur);
}, 0);

In order to process the entire master array, you can map() it to lengths:

var arr = [
  ["Jean5", "Jean3", "Paul2", "Jean6", "", "Paul4", "Jean", "peirre4", ""],
  ["Paul5", "peirre6", "peirre3", "", "Jean4", "Paul", "peirre5", "Jean2", ""],
  ["Just1", "", ""]
];

var lengths = arr.map(function(sub) {
  return sub.reduce(function(prev, cur) {
    return prev + (!!cur);
  }, 0);
});
document.write('[' + lengths.join('], [') + ']');

Get number of non-empty elements from nested arrays

4 Answers4

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