Develop Reference

Not able to send value to frontend [duplicate]

I must be missing something here, but the following code (Fiddle) returns an empty string:
var test = new Array();
test['a'] = 'test';
test['b'] = 'test b';
var json = JSON.stringify(test);
alert(json);
What is the correct way of JSON'ing this array?

JavaScript arrays are designed to hold data with numeric indexes. You can add named properties to them because an array is a type of object (and this can be useful when you want to store metadata about an array which holds normal, ordered, numerically indexed data), but that isn't what they are designed for.
The JSON array data type cannot have named keys on an array.
When you pass a JavaScript array to JSON.stringify the named properties will be ignored.
If you want named properties, use an Object, not an Array.
const test = {}; // Object
test.a = 'test';
test.b = []; // Array
test.b.push('item');
test.b.push('item2');
test.b.push('item3');
test.b.item4 = "A value"; // Ignored by JSON.stringify
const json = JSON.stringify(test);
console.log(json);

Nice explanation and example above. I found this (JSON.stringify() array bizarreness with Prototype.js) to complete the answer. Some sites implements its own toJSON with JSONFilters, so delete it.
if(window.Prototype) {
delete Object.prototype.toJSON;
delete Array.prototype.toJSON;
delete Hash.prototype.toJSON;
delete String.prototype.toJSON;
}
it works fine and the output of the test:
console.log(json);
Result:
"{"a":"test","b":["item","item2","item3"]}"

I posted a fix for this here
You can use this function to modify JSON.stringify to encode arrays, just post it near the beginning of your script (check the link above for more detail):
// Upgrade for JSON.stringify, updated to allow arrays
(function(){
// Convert array to object
var convArrToObj = function(array){
var thisEleObj = new Object();
if(typeof array == "object"){
for(var i in array){
var thisEle = convArrToObj(array[i]);
thisEleObj[i] = thisEle;
}
}else {
thisEleObj = array;
}
return thisEleObj;
};
var oldJSONStringify = JSON.stringify;
JSON.stringify = function(input){
if(oldJSONStringify(input) == '[]')
return oldJSONStringify(convArrToObj(input));
else
return oldJSONStringify(input);
};
})();

Another approach is the JSON.stringify() replacer function param. You can pass a 2nd arg to JSON.stringify() that has special handling for empty arrays as shown below.
const arr = new Array();
arr.answer = 42;
// {"hello":"world","arr":{"answer":42}}
JSON.stringify({ hello: 'world', arr }, function replacer(key, value) {
if (Array.isArray(value) && value.length === 0) {
return { ...value }; // Converts empty array with string properties into a POJO
}
return value;
});

Alternatively you can use like this
var test = new Array();
test[0]={};
test[0]['a'] = 'test';
test[1]={};
test[1]['b'] = 'test b';
var json = JSON.stringify(test);
alert(json);
Like this you JSON-ing a array.

Json has to have key-value pairs. Tho you can still have an array as the value part. Thus add a "key" of your chousing:
var json = JSON.stringify({whatver: test});

Get Url string parameter as JSON object

I was wondering if it is possible to get the url parameter as JSON object using window object.
For ex. I have the url "/#/health?firstName=tom&secondName=Mike"
and get the value as {"firstName": "tom", "secondName": "Mike"}
I tried to explore the window object but could not find any help.
I think I can try parsing the string firstName=tom&secondName=Mike and convert this to json but this doesn't look like a great approach. BTW if there are smart way to parse, that too will be appreciated.
Please let me know if I should provide any more information.

In Angular you can get the URL with:
this.router.url
Once you've got the URL, you should use the very popular (14 mill downloads a week) npm qs module:
var qs = require('qs');
var obj = qs.parse('firstName=tom&secondName=Mike');
returns:
{
firstName: 'tom'
secondName: 'mike'
}

Using straight javascript first get the params and then convert them into an object:
<script type="text/javascript">
// params will be an object with key value pairs based on the url query string
var params = paramsToObject();
console.log(params);
// Get the parameters by splitting the url at the ?
function getParams() {
var uri = window.location.toString();
if (uri.indexOf("?") > 0) {
var params = uri.substring(uri.indexOf("?") + 1, uri.length);
return params;
}
return "";
}
// Split the string by & and then split each pair by = then return the object
function paramsToObject() {
var params = getParams().split("&");
var obj = {};
for (p in params) {
var arr = params[p].split("=");
obj[arr[0]] = arr[1];
}
return obj;
}
</script>
If using Angular:
You can use the qs npm module suggested in the answer by danday74.

const str = 'abc=foo&def=%5Bbar%5D&xyz=5'
// reduce takes an array and reduces it into a single value
const nameVal = str.split('&').reduce((prev, curr) => {
// see output here in console for clarity:
console.log('curr= ', curr, ' prev = ', prev)
prev[decodeURIComponent(curr.split('=')[0])] = decodeURIComponent(curr.split('=')[1]);
return prev;
}, {});
// invoke
console.log(nameVal);

str.split to json with names

I have taken a string that is "title:artist" and used str.split :
res = song.split(":");
Which gives me an output of :
["Ruby","Kaiser Chiefs"]
I was wondering how I could add name to this so that it appears as :
["name":"Ruby", "artist":"Kaiser Chiefs"]

var res = song.split(':');
var jsonString = JSON.stringify({ name: res[0], artist: res[1] });
You can find more information about how to use JSON.stringify here but basically what it does is takes a JavaScript object (see how I'm passing the data as an object in my answer) and serializes it into a JSON string.
Be aware that the output is not exactly as you have described in your question. What you have is both invalid JavaScript and invalid JSON. The output that I have provided will look more along the lines of {"name":"Ruby", "artist":"Kaiser Chiefs"}. Notice how there is {} instead of [].

["name":"Ruby", "artist":"Kaiser Chiefs"] isn't a valid format I guess you want to create an object so you could use just the split like :
var my_string = "Ruby:Kaiser Chiefs";
var my_string_arr = my_string.split(':');
var my_object = {'name': my_string_arr[0],"artist": my_string_arr[1]};
console.log(my_object);
Or also assign the values to the attributes separately like:
var my_string = "Ruby:Kaiser Chiefs";
var my_string_arr = my_string.split(':');
var my_object = {};
my_object.name = my_string_arr[0];
my_object.artist = my_string_arr[1];
console.log(my_object);
Hope this helps.

What you're looking for is: Object. Here is how you do it:
var str = "Ruby:Kaiser Chiefs";
var res = str.split(':');
// this is how to declare an object
var myObj = {};
// this is one way to assigne to an object
// using: myObj["key"] = value;
myObj["name"] = res[0];
// this is another way to assign to an object
// using: myObj.key = value;
myObj.artist = res[1];
console.log(myObj);

JavaScript Custom JSON Names Childs

I am trying to create a JSON Array:
let someJSON = {};
someJSON["number1"] = "someString";
works. But when I want to set a "Child" to number1 it fails:
someJSON["number1"]["date"] = "19.01.2017";
I tried some things but its not working :(
I need to create the JSON like this because I needs variables as parents

I am trying to create a JSON Array:
let someJSON = {};
someJSON["number1"] = "someString";
That's not a JSON array, that's a JavaScript object.
But when I want to set a "Child" to number1 it fails:
someJSON["number1"]["date"] = "19.01.2017";
That's because you're setting a property on a string primative. That will temporarily promote the string primative to an object, set the property, and then throw away the object, effectively doing nothing.
To make someJSON.number an object, create an object just like you did for someJSON and add properties to it. Or you can do it all at once:
let obj = {
number1: {
date: "19.01.2017"
}
};
If you want "someString" in there somewhere, just put it on another property:
let obj = {
number1: {
str: "someString",
date: "19.01.2017"
}
};

You have to create the "number1" object first. Note that you won't be able to set a string value for "number1" as it is now an object.
let someJSON = {};
someJSON["number1"] = {};
someJSON["number1"]["date"] = "19.01.2017";

accessing JSON value if key is array element

suppose i receive JSON object from the server as this
{ "asdf[zxcv]": "qwer" }
how do i access asdf, zxcv, and qwer in javascript, so i can use the object this way ?
theobj.asdf[zxcv] = 'qwer'

Bracket notation is not in the JSON RFC. You can only read it as string.
var simpleObj = {
"simpleKey": "simpleValue"
}
console.log(simpleObj)
var advObj = {
"advKey[1]": "advValue"
}
console.log(JSON.parse(advObj)); // SyntaxError
console.log(advObj.advKey[1]) // TypeError
console.log(advObj["advKey[1]"]) // can only read as string

You would need to refactor the source JSON into something more meaningful so you can access the values in regular JavaScript way.
Run the following snippet to check how you can solve the issue:
var x = '{ "asdf[zxcv]": "qwer" }';
var y = JSON.parse(x);
var result = Object.keys(y).reduce(function(result, key) {
var parentKey = key.substring(0, key.indexOf("["));
var innerKey = /[a-z]+\[([a-z]+)\]/i.exec(key)[1];
if (!result.hasOwnProperty(key))
result[parentKey] = {};
result[parentKey][innerKey] = y[key];
return result;
}, {});
document.getElementById("structure").textContent = JSON.stringify(result);
var zxcv = result["asdf"]["zxcv"];
document.getElementById("someValue").textContent = zxcv;
<h2>Refactored data structure as nested objects:</h2>
<div id="structure"></div>
<h2>Accessing some value: result["asdf"]["zxcv"] or result.asdf.zxcv</h2>
<div id="someValue"></div>
It's all about creating nested objects to represent the associative keys in the source JSON properties representing a conceptual associative array...

This is one of the way to access all elements without reconstructing object.
jQuery.each(JSON.parse('{ "asdf[zxcv]": "qwer" }'), function(index, value) {
var i = index;// i = "asdf[zxcv]"
var v = value;// v = "qwer"
var iOfInnerValue = (/\[(.*?)\]/g).exec(i)[1];// innerValue = "zxcv"
var iOfOuterValue = index.replace("["+(/\[(.*?)\]/g).exec(i)[1]+"]",""); // outerValue = "asdf"
});

You'll need to assign the data to a variable and then you can use Object keys to get the key which is the part before the :. Here's an example.
var j = { "asdf[zxcv]": "qwer" };
console.log(Object.keys(j)); //["asdf[zxcv]"]
console.log(j); //{asdf[zxcv]: "qwer"}