Javascript: How to Pass Object by Value

JavaScript: How to pass object by value?

Not really.

Depending on what you actually need, one possibility may be to set o as the prototype of a new object.

var o = {};
(function(x){
    var obj = Object.create( x );
    obj.foo = 'foo';
    obj.bar = 'bar';
})(o);

alert( o.foo ); // undefined

So any properties you add to obj will be not be added to o. Any properties added to obj with the same property name as a property in o will shadow the o property.

Of course, any properties added to o will be available from obj if they're not shadowed, and all objects that have o in the prototype chain will see the same updates to o.

Also, if obj has a property that references another object, like an Array, you'll need to be sure to shadow that object before adding members to the object, otherwise, those members will be added to obj, and will be shared among all objects that have obj in the prototype chain.

var o = {
    baz: []
};
(function(x){
    var obj = Object.create( x );

    obj.baz.push( 'new value' );

})(o);

alert( o.baz[0] );  // 'new_value'

Here you can see that because you didn't shadow the Array at baz on o with a baz property on obj, the o.baz Array gets modified.

So instead, you'd need to shadow it first:

var o = {
    baz: []
};
(function(x){
    var obj = Object.create( x );

    obj.baz = [];
    obj.baz.push( 'new value' );

})(o);

alert( o.baz[0] );  // undefined

Pass object into function as parameter in Javascript

Yes. In javascript, objects are passed by reference. So, if you change the value of an object within the function, it changes it back outside of the function.

If you did something like this, though, it wouldn't be the case:

function setWhite(obj){
  obj = {
    color: "white",
    size: "M"
  }
}

var shirt = {
  color: "red",
  size: "L"
}

setWhite(shirt);

console.log(shirt); // shirt will remain red / L

Note the difference is that I'm reassigning obj inside the setWhite() method, so the original obj is lost to that function.

This is an important concept to understand, since it can have disturbing and unintended consequences if you let it slip your mind, accidentally changing the value on objects that you didn't want to change, just temporarily manipulate the data for some other purpose. It's especially important to keep in mind when you start working with async functions. Async functions happen in the background, and you have to specify when to 'await' for them. If you call an async function expecting it to change your objects values, but don't await it, your object might not have the updated values yet when you go to use them later in the code that calls the async function.

Similarly, if you call an async function, but don't await it, and later change the object that was passed in, by the time the async function goes to use the values from that object, they could be different than you intended when you called it.

How to pass object name value pair as a parameter to the method?

You can filter the array of objects from the response using Array.prototype.filter. Then you can pass the values from those "DSTR_NR" objects to your method. If you want to only have the values from each value key in the filtered array of objects, just use Array.prototype.map.

let result = [
  {name: "Desc", value: "7777 - Florida Hurricane"},
  {name: "DSTR_NR", value: "7777"},
  {name: "Desc", value: "7172 - Virginia Severe Storm(s)"},
  {name: "DSTR_NR", value: "7172"},
  {name: "Desc", value: "7002 - Maryland Hurricane"},
  {name: "DSTR_NR", value: "7002"}
];

// array of "DSTR_NR" key-value pairs
let disasterVals = result.filter(i => i.name === "DSTR_NR");
console.log(disasterVals);

// array of `value`'s
let values = disasterVals.map(i => i.value);
console.log(values);

function someMethod(val) {
  return "Disaster Val: " + val;
}

// access value from array of objects
console.log(someMethod(disasterVals[0].value));

// or access value from array of `value`'s
console.log(someMethod(values[1]));
console.log(someMethod(values[2]));

How can I pass an object by value to a function in nodejs/javascript?

You cannot control how JS passes variables (afaik), so it will always pass by reference (some conditions may apply). The proper way to do this is to create a copy of the object and pass that in.

This functionality is built in to jQuery (not terribly hard to replicate).

var clone = function(object) { return $.extend(true, {}, object) };

This will create a deep copy of the object which is safe to pass into methods that may have unintended side-effects.

Pass to method object values as arguments

You can use the spreading operator to spread the values:

someFunct(...Object.values(Obj));

Pass object to function in javascript via html button

In my opinion, you should be passing the id instead of the object, doing a remove over a DOM element doesn't make much sense.

Refresh the events on the calendar filtering that id.

var calendar = null;  
function test(id) {
    if (confirm("Are you sure you want to remove it?")) {
        alert(id);
        if(calendar!=null){
            var eventToRemove = calendar.getEventById(id);
            eventToRemove.remove();
        }
    }
 }
    
    document.addEventListener("DOMContentLoaded", function () {
        var calendarEl = document.getElementById("calendar");
    
        calendar = new FullCalendar.Calendar(calendarEl, {
            locale: "it",
            headerToolbar: {
                right: "today prev next",
                center: "title",
                left: ""
            },
            initialView: "listDay",
            views: {
                listDay: {
                    type: "listWeek",
                    dayCount: 1
                }
            },
    
            headerToolbar: {
                left: "prev,next today",
                center: "title"
            },
    
            events: [
                { id: "1", title: "Default title", start: "2022-06-17 19:00" },
    
                {
                    id: "2",
                    start: "2022-06-17 09:00",
                    title: "Event 2"
                }
            ],
            eventContent: function (args) {
                id = args.event.id;
                let event = calendar.getEventById(id);
                // pass the Id instead of the object
                const text =
                    args.event._def.title +
                    '<button style="float:right" onclick="test('+event.id+')">delete</button>';
    
                return {
                    html: text
                };
            }
        });
    
        calendar.render();
    });

javascript pass object as reference

In JavaScript objects are always passed by copy-reference. I'm not sure if that's the exactly correct terminology, but a copy of the reference to the object will be passed in.

This means that any changes made to the object will be visible to you after the function is done executing.

Code:

var obj = {  a: "hello"};
function modify(o) {  o.a += " world";}
modify(obj);console.log(obj.a); //prints "hello world"

Pass object to javascript function

The "braces" are making an object literal, i.e. they create an object. It is one argument.

Example:

function someFunc(arg) {
    alert(arg.foo);
    alert(arg.bar);
}

someFunc({foo: "This", bar: "works!"});

the object can be created beforehand as well:

var someObject = {
    foo: "This", 
    bar: "works!"
};

someFunc(someObject);

I recommend to read the MDN JavaScript Guide - Working with Objects.

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