Get key and value of a JavaScript array into variable

• Use for-loop instead of for-in to iterate array.

• Use Object.keys to get keys of object

var arr = [{
  one: 'one'
}, {
  two: 'two'
}];

for (var i = 0, l = arr.length; i < l; i++) {
  var keys = Object.keys(arr[i]);
  for (var j = 0, k = keys.length; j < k; j++) {
    console.log("Key:" + keys[j] + "  Value:" + arr[i][keys[j]]);
  }
}

I think you have two main options to get keys of an object using Object.keys these are: forEach; or a simple for.

1. Use forEach

If you're using an environment that supports the Array features of ES5 (directly or using a shim), you can use the new forEach:

var myarray = [{one: 'one'}, {two: 'two'}];

myarray.forEach(function(item) {
  var items = Object.keys(item);
  items.forEach(function(key) {
   console.log('this is a key-> ' + key + ' & this is its value-> ' + item[key]);
 });
});

forEach accepts an iterator function and, optionally, a value to use as this when calling that iterator function (not used above). The iterator function is called for each entry in the array, in order, skipping non-existent entries in sparse arrays. Although

forEach has the benefit that you don't have to declare indexing and value variables in the containing scope, as they're supplied as arguments to the iteration function, and so nicely scoped to just that iteration.

If you're worried about the runtime cost of making a function call for each array entry, don't be; technical details.

2. Use a simple for

Sometimes the old ways are the best:

var myarray = [{one: 'one'}, {two: 'two'}];

for (var i = 0, l = myarray.length; i < l; i++) {
  var items = myarray[i];
  var keys = Object.keys(items);
  for (var j = 0, k = keys.length; j < k; j++) {
    console.log('this is a key-> ' + keys[j] + ' & this is its value-> ' + items[keys[j]]);
  }
}

Depending on your construction, you can do

const arr = [{ key1: 'val1' }, { key2: 'val2' }]

arr.forEach((a, i) =>
  console.log(i, [{ key: Object.keys(a) }, { val: Object.values(a) }])
)

and to answer your question

arr.forEach((a, i) =>
  alert("Key is "+ Object.keys(a) + ", value is " +  Object.values(a))
)

am trying to get the key or value to a variable and print it.

then you could

var myarry = [{ one: 'one' }, { two: 'two' }];

for (var key in myarry) {
  var value = myarry[key];
  console.log(key, value)
}

you can do it in this way

const a = [{ one: 'one' }, { two: 'two' }];

a.forEach(function(value,key) {
   console.log(value,key);
});

You can take key and value in a variable and use them.

Here's an interesting way to do it.

const arr = [{ one: 'one' }, { two: 'two' }];

Object.entries(arr).forEach(([_, obj]) => {
  const key = Object.keys(obj)[0];
  console.log(`Key is ${key}, value is ${obj[key]}.`);
});