Assign an array value to another array called dynamically

Question

I've got an array like this

pages['name'] = "Home";
pages['childs'][0]['name'] = "Sub page 1";
pages['childs'][1]['name'] = "Sub page 2";
pages['childs'][2]['name'] = "Sub page 3";
pages['childs'][2]['childs'][0]['name'] = "Sub sub page 1";

My problem is that I need to change portions of the array for example.

pages['childs'][0] = otherarray;
// or
pages['childs'][2]['childs'][0] = otherarray;

Obviously if otherarray was a string I can easily do something like

eval('pages' + where + ' = "' + stringvalue + '"');

But I've an array as value so I can't do

eval('pages' + where + ' = "' + otherarray + '"');

because the code executed will be

pages['childs'][0] = [object object];

What's the solution? Thanks

What's the question? pages['childs'][0] = [object object]; is valid if you just alert it out... it just means that pages['childs'][0] contains an object. — John Green
– John Green, Commented Apr 9, 2015 at 8:44
@JohnGreen I think what he has is a variable where = "['childs'][0]" and he wants to use that to determine what to assign. — Barmar
– Barmar, Commented Apr 9, 2015 at 8:45
In pseudo code I've to do something like this. eval('pages' + where) = otherarray; — Claudio Ɯǝıs Mulas
– Claudio Ɯǝıs Mulas, Commented Apr 9, 2015 at 8:46
You need to write a parser for where. Then you can iterate down the object levels with those keys, and finally assign otherarray. — Barmar
– Barmar, Commented Apr 9, 2015 at 8:47
@Barmar - Then the first issue is that we're attempting to use eval. : ) — John Green
– John Green, Commented Apr 9, 2015 at 8:49

John Green · Accepted Answer · 2015-04-09 09:07:11Z

0

Rather than screw around with eval and stringifying things, you should just build an accessor. Many would agree that using eval like this is just bad practice in every way. I don't know if combining it with stringify makes it worse, but it certainly feels dirty.

Here's a basic, fairly stupid accessor, but it should give you the idea.

// Arguments:  array to modify; new value; series of nested array keys.
function modifyArray(base, value){
   var refObj = base;
   for (var ii=2, max=arguments.length; ii < max; ii++){
       if (!refObj) {
          return false;  // we supplied an invalid key.
       }
       if (ii == max-1){
           refObj[arguments[ii]] = value;
           return true;
       }
       refObj = refObj[arguments[ii]];
   }
   return false; // probably forgot to include keys.
}

modifyArray(pages, otherarray, 'childs', 2, 'childs', 0);

http://jsfiddle.net/2ts78brg/

answered Apr 9, 2015 at 9:07

John Green

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2 Comments

Claudio Ɯǝıs Mulas Over a year ago

This is not a solution. I need even a parse for the var where.

John Green Over a year ago

I don't know where 'where' comes from. At the end of the day, its your code, you can build it and maintain it however you want -- but from my 20 years of code-writing, I can almost guarantee you that your eval/stringify solution will come back and bite you badly at some point.

Claudio Ɯǝıs Mulas · Accepted Answer · 2015-04-09 09:04:59Z

-1

For me this solution works

eval("pages" + where + " = JSON.parse('" + JSON.stringify(otherarray) + "')");

It sounds more like a workaround then a solution but it works and for me it's enough.

answered Apr 9, 2015 at 9:04

Claudio Ɯǝıs Mulas

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