Develop Reference

How to add an element to multi-dimensional JSON array if the element key is a variable

There is a JSON file with an array like
{
"general_array":[
{"key_1":["a","b","c"]}
]
}
I want to add an element to the array e.g.
{"key_2":["d","e","f"]}
but the value of new key I get from a variable e.g.
var newKey = 'key_2';
I'm trying to add the element to the existed array as following
// ... getting file content
// var jsonFileContent = '{"general_array":[{"key_1":["a","b","c"]}]}';
var jsonObj = JSON.parse(jsonFileContent);
var newKey = 'key_2';
jsonObj.general_array.push({newKey:['d','e','f']});
var newJsonFileContent = JSON.stringify(jsonObj);
// and rewrite the file ...
// console.log(newJsonFileContent);
But in the file I get
{
"general_array":[
{"key_1":["a","b","c"]},
{"newKey":["d","e","f"]}
]
}
i.e. as the new element key I get the NAME of variable, but I need its VALUE
How to add the value?
UPDATED
The solution with [newKey] works in most of browsers, but it doesn't work in Internet Explorer 11
I need a solution to be working in IE11 too, so the question is still actual

You can use [newKey] to get the value of the variable as a key name:
var jsonFileContent = `
{
"general_array":[
{"key_1":["a","b","c"]}
]
}`;
var jsonObj = JSON.parse(jsonFileContent);
var newKey = 'key_2';
var tempObj = {};
tempObj[newKey] = ['d','e','f'];
jsonObj.general_array.push(tempObj);
var newJsonFileContent = JSON.stringify(jsonObj);
console.log(newJsonFileContent);

To use the value of a variable as a JSON key, enclose it in square brackets, like so:
{[newKey]:['d','e','f']}
let jsonFileContent = '{"general_array":[{"key_1":["a","b","c"]}]}';
let jsonObj = JSON.parse(jsonFileContent);
let newKey = 'key_2';
jsonObj.general_array.push({[newKey]:['d','e','f']});
let newJsonFileContent = JSON.stringify(jsonObj);
console.log(newJsonFileContent)
This is the computed property name syntax. It's a shorthand/syntax sugaring for someObject[someKey] = somevalue

Try changing this line:
jsonObj.general_array.push({newKey:['d','e','f']});
For this:
var newObj = {};
newObj[newKey] = ['d','e','f'];
jsonObj.general_array.push(newObj);

Add items to a Javascript object

My app is hitting a WebAPI that returns some JSON records. I get them via jQuery AJAX and assign the JSON to a JavaScript variable. I can loop through and make changes to existing items without issue. However, how do I add more "records" to this object? I'm trying to understand the structure of the resulting variable.
Here is what I have as a test. Is this the best way?
var trustAccounts = {"accounts":[
{"entityId":12345,
"type":"IOLTA",
"nameOnAccount":"Sam Smith Trust",
"accountNumber":"987654",
"bankCode":"003",
"bankName":"Bank of Stuff",
"accountDate":"12/15/2014",
"status":"A",
"exempt":"N",
"accountId":142922,
"action":"U"}]};
var newaccount = {};
newaccount.entityId = 23456;
newaccount.type = "IOLTA";
newaccount.nameOnAccount = "John Smith Trust";
newaccount.accountNumber = "789456";
newaccount.bankCode = "003";
newaccount.bankName = "Bank of Stuff";
newaccount.accountDate = "12/15/2014";
newaccount.status = "A";
newaccount.exempt = "N";
newaccount.accountId = 142923;
newaccount.action = "U";
trustAccounts.accounts.push(newaccount);
console.log(trustAccounts);

So if we name the returned variable object we can simply create new elements using object.newItemName. Eg below:
object.newItemName = 'Hello World'

You just add them, as if they already existed. A JSON-parsed object is just a normal JavaScript object.
let obj = {};
obj.newProp = 5;
console.log(obj.newProp); // 5
obj['newProp'] = 4;
console.log(obj.newProp); // 4
You can set them in two ways, with the dot-notation or with square brackets ([]). The dot-notation way, the value after the dot is what it's called. The square bracket can accept a string or variable, so you can use it to set a property to a specific name.
If you need to nest things, you have to create each level. For example, if you wanted to set obj.something.aValue, you could do something like this:
let obj = {};
obj.something = {};
obj.something.aValue = 5;
Or, you can also do it in fewer shots, depending what you're doing:
let obj = {
something: {
aValue = 5;
}
};

Create variables based on array

I have the following array and a loop fetching the keys (https://jsfiddle.net/ytm04L53/)
var i;
var feeds = ["test_user_201508_20150826080829.txt:12345","test_user_list20150826:666","test_list_Summary20150826.txt:321"];
for (i = 0; i < feeds.length; i++) {
var feed = feeds[i];
alert(feed.match(/\d+$/));
}
The array will always contain different number of keys, What I would like to do is either use these keys as variables and assign the value after the : semicolon as its value or just create a new set of variables and assign the values found on these keys to them.
How can I achieve this? so that I can then perform some sort of comparison
if (test_user > 5000) {dosomething}
update
Thanks for the answers, how can I also create a set of variables and assign the array values to them? For instance something like the following.
valCount(feeds.split(","));
function valCount(t) {
if(t[0].match(/test_user_.*/))
var testUser = t[0].match(/\d+$/);
}
Obviously there is the possibility that sometimes there will only be 1 key in the array and some times 2 or 3, so t[0] won't always be test_user_
I need to somehow pass the array to a function and perform some sort of matching, if array key starts with test_user_ then grab the value and assign it to a define variable.
Thanks guys for all your help!

You can't (reasonably) create variables with dynamic names at runtime. (It is technically possible.)
Instead, you can create object properties:
var feeds = ["test_user_201508_20150826080829.txt:12345","test_user_list20150826:666","test_list_Summary20150826.txt:321"];
var obj = {};
feeds.forEach(function(entry) {
var parts = entry.split(":"); // Splits the string on the :
obj[parts[0]] = parts[1]; // Creates the property
});
Now, obj["test_user_201508_20150826080829.txt"] has the value "12345".
Live Example:
var feeds = ["test_user_201508_20150826080829.txt:12345","test_user_list20150826:666","test_list_Summary20150826.txt:321"];
var obj = {};
feeds.forEach(function(entry) {
var parts = entry.split(":");
obj[parts[0]] = parts[1];
});
snippet.log(obj["test_user_201508_20150826080829.txt"]);
<!-- Script provides the `snippet` object, see http://meta.stackexchange.com/a/242144/134069 -->
<script src="http://tjcrowder.github.io/simple-snippets-console/snippet.js"></script>

You can do it like this, using the split function:
var i;
var feeds = ["test_user_201508_20150826080829.txt:12345","test_user_list20150826:666","test_list_Summary20150826.txt:321"];
for (i = 0; i < feeds.length; i++) {
var feed = feeds[i];
console.log(feed.split(/[:]/));
}
This outputs:
["test_user_201508_20150826080829.txt", "12345"]
["test_user_list20150826", "666"]
["test_list_Summary20150826.txt", "321"]

Use the split method
var feeds = ["test_user_201508_20150826080829.txt:12345","test_user_list20150826:666","test_list_Summary20150826.txt:321"];
feedMap = {}
for (i = 0; i < feeds.length; i++) {
var temp = feeds[i].split(':');
feedMap[temp[0]] = temp[1];
}
Yields:
{
"test_user_201508_20150826080829.txt":"12345",
"test_user_list20150826":"666",
"test_list_Summary20150826.txt":"321"
}
And can be accessed like:
feedMap["test_user_201508_20150826080829.txt"]
Here is a codepen

it is not very good idea but if you really need to create variables on-the-run here's the code:
for (i = 0; i < feeds.length; i++)
{
var feed = feeds[i];
window[feed.substring(0, feed.indexOf(":"))] = feed.match(/\d+$/);
}
alert(test_user_201508_20150826080829)
Of course you cannot have any variable-name-string containing banned signs (like '.')
Regards,
Michał

How to stock array with localStorage (Chrome Extension)?

I tried to stock an array in localStorage but then I read it was impossible. So I tried that:
array = {};
array.name = $('[name="name"]').val();
array.username = $('[name="username"]').val();
array.password = $('[name="password"]').val();
alert(localStorage['accounts']);
local = JSON.parse(localStorage['accounts']);
localu = local.push(array);
alert(JSON.stringify(localu));
In fact the scripts stops at the first alert which returns '[]' (I previously put that value to check the result).
Why isn't my script working?

JavaScript, {} is an Object. [] is an Array.
var array = [] and var array = new Array() do the same thing.
An array is an ordered container of stuff, each value has an index not a key.
An object is a named container of stuff, each "stuff" has a key.
Your array is definitely an object.
var data = {};
data.name = $('[name="name"]').val();
data.username = $('[name="username"]').val();
data.password = $('[name="password"]').val();
alert(localStorage['accounts']);
// > undefined OR the value
local = JSON.parse(localStorage['accounts']);
// local contains a parsed version of localStorage['accounts']
localu = local.push(array);
// localu = 0 (push returns the length i think?)
alert(JSON.stringify(localu));
Try the following. I've not tested it, but might work.
var data = {};
data.name = $('[name="name"]').val();
data.username = $('[name="username"]').val();
data.password = $('[name="password"]').val();
if (localStorage['accounts'] == undefined) { // fixed
// does the key exist? No so create something to get us started
localu = { accounts: [] };
} else {
// the key exists! lets parse it
localu = JSON.parse(localStorage['accounts']);
}
// add the new "data" to the list
localu.accounts.push(data);
// save the results (we have to stringify it)
localStorage['accounts'] = JSON.stringify(localu);

Push to array a key name taken from variable

I have an array:
var pages = new Array();
I want to push my pages data to this array like this:
$('li.page').each(function () {
var datatype = $(this).attr('data-type');
var info = $(this).attr('data-info');
pages_order.push({datatype:info});
});
but this code doesn't replace datatype as variable, just puts datatype string as a key.
How do I make it place there actual string value as a key name?

I finally saw what you were trying to do:
var pages = new Array();
$('li.page').each(function () {
var datatype = $(this).attr('data-type');
var info = $(this).attr('data-info');
var temp = {};
temp[datatype] = info;
pages_order.push(temp);
});

$('li.page').each(function () {
//get type and info, then setup an object to push onto the array
var datatype = $(this).attr('data-type'),
info = $(this).attr('data-info'),
obj = {};
//now set the index and the value for the object
obj[datatype] = info;
pages_order.push(obj);
});
Notice that you can put a comma between variable declarations rather than reusing the var keyword.

It looks like you just want to store two pieces of information for each page. You can do that by pushing an array instead of an object:
pages_order.push([datatype, info]);

You have to use datatype in a context where it will be evaluated.
Like so.
var pages = [];
$('li.page').each(function () {
var datatype = $(this).attr('data-type'),
info = $(this).attr('data-info'),
record = {};
record[datatype] = info;
pages_order.push(record);
});
You only need one var it can be followed by multiple assignments that are separated by ,.
No need to use new Array just use the array literal []

You may add below single line to push value with key:
pages_order.yourkey = value;