I am banging my head trying to figure this out. And it should not be this hard. I am obviously missing a step.
I am pulling data from: openaq.org
The object I get back is based on a JSON object.
For now, I am using jQuery to parse the object and I am getting to the sub portion of the object that hold the specific parameter I want but I can't get to the specific key,value pair.
The object does not come back in the same order all the time. So when I tried to originally set up my call I did something like
obj.results.measurements[0].
Well since the obj can come back in an random order, I went back to find the key,value pair again and it was the wrong value, throwing my visual off.
That said, I have looked at use jQuery's find() on JSON object and for some reason can not get what I need from the object I am given by openaq.org.
One version of the object looks like this:
{"meta":{"name":"openaq-api","license":"CC BY 4.0d","website":"https://u50g7n0cbj.execute-api.us-east-1.amazonaws.com/","page":1,"limit":100,"found":1},"results":[{"location":"Metro Lofts","city":null,"country":"US","coordinates":{"latitude":39.731,"longitude":-104.9888},"measurements":[{"parameter":"pm10","value":49.9,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"µg/m³"},{"parameter":"pm1","value":24,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"µg/m³"},{"parameter":"um100","value":0,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"particles/cm³"},{"parameter":"um025","value":0.28,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"particles/cm³"},{"parameter":"um010","value":4.1,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"particles/cm³"},{"parameter":"pm25","value":41.1,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"µg/m³"}]}]}
I am trying to get the "pm25" value.
The code I have tried is this:
function getAirQualityJson(){
$.ajax({
url: 'https://api.openaq.org/v2/latest?coordinates=39.73915,-104.9847',
type: 'GET',
dataType: "json"
// data: data ,
}).done(function(json){
console.log("the json is" + JSON.stringify(json));
console.log("the json internal is" + JSON.stringify(json.results));
var obj = json.results;
var pm25 = "";
//console.log(JSON.stringify(json.results.measurements[0]["parameter"]));
$.each(json.results[0], function(i,items){
//console.log("obj item:" + JSON.stringify(obj[0].measurements));
$.each(obj[0].measurements, function(y,things){
//console.log("each measurement:" + JSON.stringify(obj[0].measurements[0].value));//get each measurement
//pm 2.5
//Can come back in random order, get value from the key "pm25"
// pm25 = JSON.stringify(obj[0].measurements[2].value);
pm25 = JSON.stringify(obj[0].measurements[0].value);
console.log("pm25 is: " + pm25); // not right
});
});
//Trying Grep and map below too. Not working
jQuery.map(obj, function(objThing)
{ console.log("map it 1:" + JSON.stringify(objThing.measurements.parameter));
if(objThing.measurements.parameter === "pm25"){
// return objThing; // or return obj.name, whatever.
console.log("map it:" + objThing);
}else{
console.log("in else for pm25 map");
}
});
jQuery.grep(obj, function(otherObj) {
//return otherObj.parameter === "pm25";
console.log("Grep it" + otherObj.measurements.parameter === "pm25");
});
});
}
getAirQualityJson();
https://jsfiddle.net/7quL0asz/
The loop is running through I as you can see I tried [2] which was the original placement of the 'pm25' value but then it switched up it's spot to the 3rd or 4th spot, so it is unpredictable.
I tried jQuery Grep and Map but it came back undefined or false.
So my question is, how would I parse this to get the 'pm25' key,value. After that, I can get the rest if I need them.
Thank you in advance for all the help.
You can use array#find and optional chaining to do this,
because we are using optional chaining, undefined will be returned if a property is missing.
Demo:
let data = {"meta":{"name":"openaq-api","license":"CC BY 4.0d","website":"https://u50g7n0cbj.execute-api.us-east-1.amazonaws.com/","page":1,"limit":100,"found":1},"results":[{"location":"Metro Lofts","city":null,"country":"US","coordinates":{"latitude":39.731,"longitude":-104.9888},"measurements":[{"parameter":"pm10","value":49.9,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"µg/m³"},{"parameter":"pm1","value":24,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"µg/m³"},{"parameter":"um100","value":0,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"particles/cm³"},{"parameter":"um025","value":0.28,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"particles/cm³"},{"parameter":"um010","value":4.1,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"particles/cm³"},{"parameter":"pm25","value":41.1,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"µg/m³"}]}]}
let found = data?.results?.[0]?.measurements?.find?.(
({ parameter }) => parameter === "pm25"
);
console.log(found);
You can iterate over measurements and find the object you need:
const data = '{"meta":{"name":"openaq-api","license":"CC BY 4.0d","website":"https://u50g7n0cbj.execute-api.us-east-1.amazonaws.com/","page":1,"limit":100,"found":1},"results":[{"location":"Metro Lofts","city":null,"country":"US","coordinates":{"latitude":39.731,"longitude":-104.9888},"measurements":[{"parameter":"pm10","value":49.9,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"µg/m³"},{"parameter":"pm1","value":24,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"µg/m³"},{"parameter":"um100","value":0,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"particles/cm³"},{"parameter":"um025","value":0.28,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"particles/cm³"},{"parameter":"um010","value":4.1,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"particles/cm³"},{"parameter":"pm25","value":41.1,"lastUpdated":"2021-08-09T20:49:38+00:00","unit":"µg/m³"}]}]}';
const json = JSON.parse(data);
let value = null;
const measurements = json?.results?.[0]?.measurements ?? null;
if(measurements)
for (const item of measurements)
if (item.parameter === 'pm25') {
value = item.value;
break;
}
if (value) {
// here you can use the value
console.log(value);
}
else {
// here you should handle the case where 'pm25' is not found
}
i have a realtime database from firebase with 9386 datasets in it (but that might change in the future)
thats why i want to know whats the "key" of the last event.
thats how i'm currently trying to get it to know: (with npm module qwest)
let order = "\u0022\u0024key\u0022";
let dbUrl = "https://example.firebaseio.com/users.json?limitToLast=1&orderBy=";
let end;
qwest.get(dbUrl + order)
.then(function(xhr, response) {
console.log(response);
end = response[9386]["username"];
console.log(end);
});
first question: why do i have to escape the quotation marks and the dollarsign?
second question: how can i get the "key" of the last item i'm checking for in the json (limitToLast=1).
json response looks like this:
{"9386":
{
"fromListA":"1",
"fromListB":"0",
"id":"9939",
"lastChecked":"2019-05-09 03:18:05",
"userid":"123456789",
"username":"username"
}
}
and i want to get the "9386" in a variabel.
Since you chose to use " to limit the dbUrl string, you can't use " inside that string's value without escaping it. A simpler way to define the string is to use ' to delimit it:
let dbUrl = 'https://example.firebaseio.com/users.json?limitToLast=1&orderBy="$key"';
To get the key of the object, use something like:
Object.keys(response)[0]
var response = {"9386":
{
"fromListA":"1",
"fromListB":"0",
"id":"9939",
"lastChecked":"2019-05-09 03:18:05",
"userid":"123456789",
"username":"username"
}
}
console.log(Object.keys(response)[0]);
I'm doing some exercises from school where is asking me to eval the class creation, I am given the html with several eval scripts. I'm supposed to create the javascript file to generate certain output.
This is the eval one:
try {
var output = eval('peter = new Person("Roger Roger")');
}
catch (err) {
var output = "[JavaScript Error] " + err.message;
}
if (output != '[Person "Roger Roger"]') {
error = true;
}
the expected output should be:
[Person "Roger Roger"]
but I'm getting
[object Object]
I've been looking around, but there isn't much information on how to evaluate the class creation.
Your help is very much appreciated.
When you coerce eval's return value to a string you get the default toString implementation.
You need to create a Person.prototype.toString method so coercion returns the output you're looking for, e.g.,
Person.prototype.toString = function() {
return "[Person " + this.name + "]";
}
var output = "" + eval('peter = new Person("Roger Roger")');
console.log(output);
> [Person Roger Roger]
OTOH, it's not super-clear to me what the assignment ultimately is.
I'm trying to achieve a function that makes the user able to save a mathematical formula that uses static variables that I've already created and save them with Local Storage.
Then the script fetches that formula from the Local Storage, does the math and displays the results on a table.
I have everything in order, except the fetching part;
as localStorage.getItem() returns a string, and converting it with parseFloat()/parseInt() only returns the first integer or NaN.
Both of this messes up the expected the results.
Is there any way I can get Objects from localStoage that contains both integers and variables?
Heres an example of a formula that should work, fetched by 5 localStorage.getItem() requests.
avgFrags*250
avgDmg*(10/(avgTier+2))*(0.23+2*avgTier/100)
avgSpots*150
log(avgCap+1,1.732)*150
avgDef*150
Any ideas or alternatives?
EDIT:
Each line represents the output of a getItem() request;
form_frag = localStorage.getItem('formula_frag');
form_dmg = localStorage.getItem('formula_dmg');
form_spot = localStorage.getItem('formula_spot');
form_cap = localStorage.getItem('formula_cap');
form_def = localStorage.getItem('formula_def');
localStorage store in a key-value store where every value is pushed to a string. If you are certent that you are handling "integers" you can push the string to a number:
var avgFrags = +localStorage.getItem('avgFrags'); // The + infront pushes the string to number.
I'm not completely sure that I understand your question.
(+"123") === 123
You can convert easily convert your strings to functions if you know the variable names before hand using Function(). The first parameter(s) are your function arguments and the last is your function body.
var func1 = Function('avgFrags', 'return avgFrags * 250;');
This is equivalent to:
function func1(avgFrags) {
return avgFrags * 250;
}
Known Function Signature
If you know what variable names will be used for each item in local storage then it should be easy for you to do what you want with function:
// from your edited question
form_frag = localStorage.getItem('formula_frag');
form_dmg = localStorage.getItem('formula_dmg');
// ... create functions
var fragsFunc = Function('avgFrags', form_frg );
var dmgFunc = Function('avgDmg', 'avgTier', form_dmg );
// ... get frags
var frags = fragsFunc (10); // frags = 2500; // if sample in storage
Unknown Function Signature
Now if you have a limited amount of variable names and you don't know which ones will be used with each function then you can do something like:
var avgFrags, avgDamage, avgTier, avgSpots, avgCap, avgDef;
// ... get from storage
form_frag = localStorage.getItem('formula_frag');
form_dmg = localStorage.getItem('formula_dmg');
// ... create functions
var fragsFunc = Function('avgFrags', 'avgDamage', 'avgTier', 'avgSpots', 'avgCap', 'avgDef', form_frag);
var dmgFunc = Function('avgFrags', 'avgDamage', 'avgTier', 'avgSpots', 'avgCap', 'avgDef', form_frag);
// ... get frags, only the first argument is used, but we don't know that.
var frags = fragsFunc (avgFrags, avgDamage, avgTier, avgSpots, avgCap, avgDef); // frags = 2500; // if sample in storage
You can make this simpler by having just one variable passed into the function which is an object that holds all of the arguments that can be passed to the function. Just have to make sure that the function writer uses that object.
var settings = {
avgFrags: 10,
avgDamage: 50,
// ...
};
var fragsFunc = Function('s', 's.avgFrags * 250');
var frags = fragsFunc (settings);
Getting parts with an regex
I am assuming that the above will get the job done, that you don't really want an object with variable names and numbers and operators.
If you just need the variable names and numbers (and operators) you can use a regex for that.
([a-z_$][\w\d]*)|([0-9]*\.?[0-9]+)|([^\w\d\s])
You can use that to create an array with each part. Also each part is grouped so you know which is a variable name, which is a number, and which is an other (parenthesis or operator)
var re = /(\w[\w\d]*)|([0-9]*\.?[0-9]+)|([^\w\d\s])/g,
match,
results;
while ((match = re.exec(localStorage.getItem('formula_frag'))) {
results.push({
text: match[0],
type: (match[1]) ? 'var' | (match[2]) ? 'number' : 'other'
})
}
You can view the output of the regex with your sample data using REY.
Yes you can set Objects in localstorage
Here is the fiddle for that - http://jsfiddle.net/sahilbatla/2z0dq6o3/
Storage.prototype.setObject = function(key, value) {
this.setItem(key, JSON.stringify(value));
}
Storage.prototype.getObject = function(key) {
var value = this.getItem(key);
return value && JSON.parse(value);
}
$(function() {
localStorage.setObject('x', {1: 2, 2: "s"})
console.log(localStorage.getObject('x'));
});
When I add items to the beats array and then console.log the User, I'm getting the correct number of items in the array. But when I check .length, I always get 1.
Trying to call the index will always give me 'undefined' like so:
Tom.beats[1]
I think I'm missing something obvious, but this is beating me. I suspect that I'm misusing the .push method but I'm unsure. Any help is greatly appreciated!
(using Chrome dev tools)
//The USER
function User(name, role){
this.beats = [ ];
this.name = name;
this.role = role;
// add beats to beats array
this.addBeats = function(beats){
return this.beats.push(beats);
};
}
// Three New Instances. Three New Users.
var Mal = new User("Mal", "Rapper");
Mal.addBeats(["love", "cash"]);
var Dan = new User("Dan", "Producer");
Dan.addBeats(["cake", "dirt", "sally-mae"]);
var Tom = new User("Tom", "Producer");
Tom.addBeats(["Fun", "Little", "Samsung", "Turtle", "PC"]);
// Check for position in beats array
console.log(Tom.beats);
console.log(Mal.beats);
console.log(Dan.beats);
console.log(Mal.beats[1]);
console.log(Dan.beats[1]);
console.log(Tom.beats[1]);
Array.push(...) takes multiple arguments to append to the list. If you put them in an array itself, this very array of "beats" will be appended.
Array.concat(...) is most likely not what you are looking for, because it generates a new array instead of appending to the existing one.
You can use [].push.apply(Array, arg_list) to append the items of the argument list:
this.addBeats = function(beats) {
return [].push.apply(this.beats, beats);
};
Spread operator
In environments that support the spread operator you may now do the following:
this.addBeats = function (beats) {
return this.beats.push(...beats);
};
Or if you need more control for overwriting etc
this.addBeats = function(beats) {
return this.beats.splice(this.beats.length, null, ...beats);
};
addBeats() should concat this.beats with the beats parameter.