How can I get a collection of keys in a JavaScript dictionary

Question

I have a dictionary  var driversCounter          quot one quot     1       quot two quot     2       quot three quot   3       quot four quot    4       quot five quot    5    Now  I need to show it in a dropdownlist  How can I get the collection of keys in my dictionary

User · Answer

This will work in all JavaScript implementations:

var keys = [];

for (var key in driversCounter) {
    if (driversCounter.hasOwnProperty(key)) {
        keys.push(key);
    }
}

Like others mentioned before you may use Object.keys, but it may not work in older engines. So you can use the following monkey patch:

if (!Object.keys) {
    Object.keys = function (object) {
        var keys = [];

        for (var key in object) {
            if (object.hasOwnProperty(key)) {
                keys.push(key);
            }
        }
    }
}

User · Answer

For new browsers  Object keys  MY DICTIONARY   will return an array of keys  Else you may want to go the old school way  var keys      for var key in dic  keys push  key

User · Answer

Use Object keys   or shim it in older browsers     const keys   Object keys driversCounter     If you wanted values  there is Object values   and if you want key and value  you can use Object entries    often paired with Array prototype forEach   like this     Object entries driversCounter  forEach   key  value     gt       console log key  value           Alternatively  considering your use case  maybe this will do it     var selectBox  option  prop   selectBox   document getElementById  drivers     for  prop in driversCounter       option   document createElement  option       option textContent   prop     option value   driversCounter prop      selectBox add option

User · Answer

If you can use jQuery then var keys         each driversCounter  function key  value        keys push key        console log JSON stringify keys     Here follows the answer    quot one quot    quot two quot    quot three quot    quot four quot    quot five quot    And this way you wouldn t have to worry if the browser supports the Object keys method or not

User · Answer

A different approach would be to using multi-dimensional arrays   var driversCounter           one   1          two   2          three   3          four   4          five   5      and access the value by driverCounter k  j   where j 0 1 in the case   Add it in a drop down list by   var dd   document getElementById  your dropdown element    for i 0 i lt driversCounter length-1 i          dd options add opt       opt text   driversCounter i  0       opt value   driversCounter i  1

User · Answer

Simply use Object keys      x000D   x000D  var driversCounter     x000D                         one   1  x000D                         two   2  x000D                         three   3  x000D                         four   4  x000D                         five   5 x000D                         x000D  console log Object keys driversCounter    x000D   x000D   x000D

User · Answer

With a modern JavaScript engine you can use Object keys driversCounter

User · Answer

To loop through the  quot dictionary quot   we call it object in JavaScript   use a for in loop  for var key in driversCounter        if driversCounter hasOwnProperty key                key                   keys   left of the  quot   quot             driversCounter key    value  right of the  quot   quot

User · Answer

As others have said  you could use Object keys    but who cares about older browsers  right  Well  I do  Try this  array keys from PHPJS ports PHP s handy array keys function  so it can be used in JavaScript  At a glance  it uses Object keys if supported  but it handles the case where it isn t very easily  It even includes filtering the keys based on values you might be looking for  optional  and a toggle for whether or not to use strict comparison     versus typecasting comparison     optional

User · Answer

One option is using Object keys    Object keys driversCounter   It works fine for modern browsers  however  Internet  Explorer supports it starting from version 9 only   To add compatible support you can copy the code snippet provided in MDN

[javascript] How can I get a collection of keys in a JavaScript dictionary?

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