construct a new array from an array by filtering out null items

Question

I am trying to construct an array looping over another array which more or less looks like this

var x = [1, null, 324, 110, null]

I am trying to loop over this and check if an item at index i is not null then it goes into a new array

var numberCollection = [];

for(var i = 0; i < x.length; i++){
    numberCollection[i] = (!!x[i]) ? x[i];
}

console.log(numberCollection)

which definitely does not work. What am I missing? I saw some examples of deleting an invalid item from an array but that is out of scope in this context

Lumi Lu · Accepted Answer · 2015-04-29 02:18:48Z

4

Try something like this,

for(var i = 0; i < x.length; i++){
    if (x[i] !== null){
      numberCollection.push(x[i]);
    }
}

edited Apr 29, 2015 at 2:18

answered Apr 29, 2015 at 2:17

Lumi Lu

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4 Comments

FreeSandwiches Over a year ago

beat me by 34 seconds.

soum Over a year ago

@ScottCorbett -- this one works..your work too. I see where my mistake was. Thanks for pointing at the right direction :-)

Matt Browne Over a year ago

Just curious, why !== instead of just !=? The type comparison seems unnecessary in this case...

Lumi Lu Over a year ago

@MattBrowne. Here stackoverflow.com/questions/359494/… the link maybe have better explaining. thanks.

FreeSandwiches · Accepted Answer · 2015-04-29 02:17:50Z

0

Let's call the first array(the one that has NULLs) A[] and the second B[]. we will also need an int count.

for(var i=0; i<A.length; i++){
    if(A[i] != NULL){
        B[count] = A[i];
        count++;
    }
}

that should do it.

answered Apr 29, 2015 at 2:17

FreeSandwiches

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Comments

Matt Browne · Accepted Answer · 2015-04-29 02:19:18Z

0

The other answers work...just to give you another option, you could use the new filter() method introduced in ECMAScript 5:

var numberCollection = x.filter(function(item) {
    return !!item;
});

Note that for this to work in IE8 and below you'll need to provide a shim for the filter() method; there's one here: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/filter#Polyfill.

answered Apr 29, 2015 at 2:19

Matt Browne

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Comments

deluged.oblivion · Accepted Answer · 2015-04-29 02:20:44Z

0

The following seemed to work fine.

var x = [1, null, 324, 110, null];
var numberCollection = [];

var k = 0;
for(i = 0; i < x.length; i++) {
    if (x[i] === null) {
        continue;
    } else {
        numberCollection[k++] = x[i];
    }
}

console.log(numberCollection);

answered Apr 29, 2015 at 2:20

deluged.oblivion

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Comments

HDN · Accepted Answer · 2015-04-29 02:22:34Z

0

This should work.

var numberCollection = [];
for(var i = 0, j = x.length; i < j; i++){
    if (x[i] !== null) {numberCollection.push(x[i])}
}

answered Apr 29, 2015 at 2:22

HDN

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