How to dynamically add values in JSON array using index - arrays

Question

I am having this format in my script
//declaration of JSON object
items= {};
items.values= [];
I need a structure like this, which is inserted automatically when the script is executed:
items :
{
key :['one', 'two', 'three', 'four'],
values: [1, 2, 3, 4]
}
Since the item.values[0] is undefined, it throws me a undefined error. Can anyone please tell me how to initialize the JSON object, such that it wont throw undefined error
I would like to insert like this:
var i=0;
item.key[i]= 'one';
item.values[i]= 1;
I am not sure whether this is the best practice, if anyone knows better way please post it!
Thanks in advance

Answer 1

You have the right idea. It looks like your property for adding keys isn't there though. Let's declare two properties, keys and values.
items= {};
items.keys = [];
items.values= [];
Our JavaScript object now looks like this
{ "keys": [], "values": [] }
var words = ['one', 'two', 'three', 'four'];
var numbers = [1,2,3,4];
You now want to iterate using a forloop. In JavaScript, arrays are 0-indexed, meaning the first element has an index of 0. That's why we initialize the i variable with a value of 0. After every iteration, we increment this variable and then check if it's less than the length of the array.
function populateObject() {
for (var i = 0; i < words.length; i++) {
items.keys.push(words[i]);
items.values.push(numbers[i]);
}
}
And then call your function
populateObject();
Here is the output
{"keys": ["one", "two", "three", "four"], "values": [1, 2, 3, 4]}