removing multiple arrays from a 2D array

Question

My web app is taking in arbitrarily large 2D arrays that sometimes look something like this:

var multiArray = [["","","",""],[1,2,3],["hello","dog","cat"],["","","",""]];

I want to write a function to take out every array inside of multiArray that is comprised entirely of quotes. In other words, any array that looks like this:

["","","",""]

should be deleted from multiArray.

I tried writing the following function, but the problem with using splice in a for loop is that splicing will change the length of the array, and I end up trying to access undefined elements. Please help!

Thanks!

Here's the incorrect function I wrote:

function cleanWhitespace(arrayOfArrays) {
    var i;
    var arrayOfArraysLength = arrayOfArrays.length;
    for (i = 0; i < arrayOfArraysLength; i++) {
        var cleanedArray = $.grep(arrayOfArrays[i], function(element) {
                                return element != ""
                            });
        if (cleanedArray.length == 0)  {
            arrayOfArrays.splice(i, 1);
        }
    }
    return arrayOfArrays;
};

iterate in reverse, or do i-- every time you do a .splice(). This is a very common issue. — cookie monster
– cookie monster, Commented Jul 15, 2014 at 17:22

Karl-André Gagnon · Accepted Answer · 2014-07-15 17:19:11Z

4

You can use $.grep :

multiArray = $.grep(multiArray, function(v){
    return v.join('');
});

Fiddle : http://jsfiddle.net/scZcB/

answered Jul 15, 2014 at 17:19

Karl-André Gagnon

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1 Comment

user3757174 Over a year ago

Thank you! Very elegant solution.

Amir Popovich · Accepted Answer · 2014-07-15 17:13:40Z

1

on the fly:

var multiArray = [["","","",""],[1,2,3],["hello","dog","cat"],["","","",""]];
var outputArr = removeQuoteArrays(multiArray);
console.log(outputArr);

function removeQuoteArrays(arr) {
    var outputArr = [];

    for (var i = 0; i < arr.length; i++) {
        var currArr = arr[i];
        var isAllQuotes = true;
        for (var j = 0; j < currArr.length; j++) {
            if (currArr[j] != "") {
                isAllQuotes = false;
                break;
            }
        }

        if (!isAllQuotes) {
            outputArr.push(currArr);
        }
    }
    return outputArr;
}

Here's a JSFiddle.

answered Jul 15, 2014 at 17:13

Amir Popovich

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Comments

parchment · Accepted Answer · 2014-07-15 17:14:42Z

1

Create a new array instead.

// Only add if...
cleanedArray = multiArray.filter(function(arr){
    // Some elements are not blank
    return arr.some(function(e){ return e !== "" }) 
})

answered Jul 15, 2014 at 17:14

parchment

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2 Comments

Dan Korn Over a year ago

A bit more succinctly: var cleanedArray = multiArray.filter(function(arr){return arr.some(String)});

cookie monster Over a year ago

That's not always possible. Sometimes there are multiple references to the original Array, which means they won't see the update.

Robbie · Accepted Answer · 2014-07-15 17:20:29Z

0

I added a length check to your function to break out of the loop if the index reaches the array length:

if (i >= arrayOfArrays.length)
      break;

Which makes:

function cleanWhitespace(arrayOfArrays) {
    var i;
    var arrayOfArraysLength = arrayOfArrays.length;
    for (i = 0; i < arrayOfArraysLength; i++) {
        var cleanedArray = $.grep(arrayOfArrays[i], function(element) {
                                return element != ""
                            });
        if (cleanedArray.length == 0)  {
            arrayOfArrays.splice(i, 1);
            if (i >= arrayOfArrays.length)
                break;
        }
    }
    return arrayOfArrays;
};

answered Jul 15, 2014 at 17:20

Robbie

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Comments

Razip · Accepted Answer · 2014-07-15 17:25:58Z

0

var multiArray = [["","","",""],[1,2,3],["hello","dog","cat"],["","","",""]];

function cleanWhitespace(arrayOfArrays) {
    for (var i = 0; i < arrayOfArrays.length; i++) {
        var emptyElements = 0;

        for (var j = 0; j < arrayOfArrays[i].length; j++ ) {
            if (arrayOfArrays[i][j] === "") {
                emptyElements++;
            }
        }

        if (emptyElements === arrayOfArrays[i].length) {
            arrayOfArrays.splice(i, 1);
        }
    }

    return arrayOfArrays;
}

console.log(cleanWhitespace(multiArray));

http://jsfiddle.net/4Jfr9/

answered Jul 15, 2014 at 17:25

Razip

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