Filter an array in javascript with value 0

Question

I got an array like this:

let arr = ['1','2','0','3','0',undefined,'0',undefined,'3','',''];

In order to filter the 'undefined' and '' element of this array and convert it to a number, I do like this:

arr = arr.filter(function(e){
    if(e){
        return parseInt(e);
    }
});

I got:

[1,2,3,3]

The 0 has also been filtered because 'return 0' means 'return false';

I want to know how do you normally do with this kind of problem?

Update:

I saw the following answers propose many useful ways. I learned a lot from it.

And if the element in the array need to be a number, not a string, should I traverse the array again? Or there is an alternative one-step method?

You mean "number" or "integer"?

tsh
– tsh

2018-01-12 07:28:23 +00:00
Commented Jan 12, 2018 at 7:28 — tsh
– tsh, Commented Jan 12, 2018 at 7:28

gurvinder372 · Accepted Answer · 2018-01-12 07:12:43Z

4

Replace

return parseInt(e);

with

return !isNaN(e);

Demo

var arr = ['1','2','0','3','0',undefined,'0',undefined,'3','',''];
var output = arr.filter(function(e){
    if(e){
        return !isNaN(e);
    }
});
console.log( output );

Edit

For converting the values to Number as well, just add .map( Number ) to the filter output

Demo

var arr = ['1','2','0','3','0',undefined,'0',undefined,'3','',''];
var output = arr.filter(function(e){
    if(e){
        return !isNaN(e);
    }
}).map( Number );
console.log( output );

edited Jan 12, 2018 at 7:12

answered Jan 12, 2018 at 6:47

gurvinder372

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8 Comments

zzm Over a year ago

!isNaN(e); It can't filter the empty string.

gurvinder372 Over a year ago

@zhaozhiming It does, please check the demo as well.

Kosh Over a year ago

if(e){ filters empty strings, not !isNaN

gurvinder372 Over a year ago

@KoshVery I meant that my answer is filtering out empty strings, not !isNaN alone, which was already happening for OP.

Kosh Over a year ago

Sorry for misunderstanding! and you forgot the conversion to numbers...

|

Nina Scholz · Accepted Answer · 2018-01-12 07:02:22Z

3

You could chain the wanted conditions.

let array = ['1', '2', '0', '3', '0', undefined, '0', undefined, '3', '', ''];

array = array
    .filter(Boolean) // get only truthy values
    .map(Number);    // convert all values to number
    
console.log(array);

answered Jan 12, 2018 at 7:02

Nina Scholz

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Comments

Steven · Accepted Answer · 2018-01-12 07:00:57Z

3

It's easy with array chain-functions:

let arr = ['1', '2', '0', '3', '0', undefined, '0', undefined, '3', '', '']
  // filter valid elements (undefined and '' evaluates to false)
  .filter(e => e)
  // to exclude '0' from the list, do a bitwise-or
  //.filter(e => e|0)
  // cast into numbers
  .map(e => e * 1);

console.log(arr);

edited Jan 12, 2018 at 7:00

answered Jan 12, 2018 at 6:55

Steven

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Comments

Suresh Atta · Accepted Answer · 2018-01-12 06:49:28Z

2

With slight change

let arr = ['1','2','0','3','0',undefined,'0',undefined,'3','',''];


arr = arr.filter(function(e){
    if( parseInt(e) >=0 ){
        return  e;
    }
});
console.log(arr);

answered Jan 12, 2018 at 6:49

Suresh Atta

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1 Comment

htxu Over a year ago

thanks, the elements in the result array are strings, and I want them to be numbers, should I traverse the array again? Or is there an alternative one-step way?

Lewis · Accepted Answer · 2018-01-12 06:59:51Z

0

let arr = ['1','2','0','3','0',undefined,'0',undefined,'3','',''];
let result = [];
for(let item of arr) {
  let num = +item;
  if(item === '' || Number.isNaN(num)) {
    continue;
  }
  result.push(num);
}
console.log(result);

answered Jan 12, 2018 at 6:59

Lewis

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Comments

guest271314 · Accepted Answer · 2018-01-12 07:01:13Z

0

You can use RegExp.prototype.test() with RegExp /^\d+$/ to check if the value is one or more digits

arr = arr.filter(n => /^\d$/.test(n))

answered Jan 12, 2018 at 7:01

guest271314

1

Comments

zhichenx · Accepted Answer · 2018-01-12 07:26:02Z

0

let arr = ['1','2','0','3','0',undefined,'0',undefined,'3','',''];

// map everything to Number (undefined becomes NaN)
// filter all valid numbers
arr = arr.map(Number).filter(e => !isNaN(e))
console.log(arr);

answered Jan 12, 2018 at 7:26

zhichenx

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