Set Array member to null instead of ""

Question

How can we set empty strings inside an array to null in JavaScript?

My array:

var myarray = [["01.01.2013","a"],["01.02.2013","b"],["01.03.2013",""]]

I need to replace the second value in the third element to null.

My attempt was to check whether a string is empty and then set it to null but that results in "null" and not null.

Out of curiosity... why? Besides that, how are you outputting the result? — Niet the Dark Absol
– Niet the Dark Absol, Commented Apr 2, 2014 at 17:46
Show your attempt so that we can explain what you did wrong. — cookie monster
– cookie monster, Commented Apr 2, 2014 at 17:47
I plot the result. I need the null in order to detect missing points and break the graph for them (jqplot). — gco
– gco, Commented Apr 2, 2014 at 17:47
that surprises me that you would get a "null" result from that since an Array doesn't have a .replace() method. — cookie monster
– cookie monster, Commented Apr 2, 2014 at 17:52

raina77ow · Accepted Answer · 2014-04-02 17:55:34Z

2

One possible approach:

myarray = myarray.map(function(el) {
  return el.map(function(v) {
    return v === '' ? null : v;
  });
});

... but I'd rather do it with a simple check, without generating tons of new arrays.

myarray.forEach(function(arr) {
  if (arr[0] === '') arr[0] = null;
  if (arr[1] === '') arr[1] = null;
});

edited Apr 2, 2014 at 17:55

answered Apr 2, 2014 at 17:49

raina77ow

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Oriol · Accepted Answer · 2014-04-02 17:47:43Z

1

In ES6 (currently negligible browser support):

myarray = myarray.map(i => i.map(i => i==='' ? null : i))

IN ES5:

myarray = myarray.map(function(i){
    return i.map(function(i){
        return i==='' ? null : i;
    })
})

answered Apr 2, 2014 at 17:47

Oriol

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Comments

Matt Eckert · Accepted Answer · 2014-04-02 18:08:07Z

1

If you are just trying to detect empty strings, you don't need to set anything to null since code inside if ("") does not execute. Just check like this: if (string) { /* string is not empty */ }.

Otherwise, if you really need the element to be null, what's wrong with just assigning it? For example:

> myarray[2][1] = null;
> console.log(myarray[2]);
["01.03.2013", null]

edited Apr 2, 2014 at 18:08

answered Apr 2, 2014 at 17:46

Matt Eckert

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