Pass object to javascript function

Question

I have recently been messing around with jQuery on my website, and I have a fairly limited knowledge of Javascript. I am beginning to like the jQuery ability to pass variables to a jQuery function inside the curly braces, like so:

$(somediv).animate({thisisone: 1, thisistwo: 2}, thisisavar);

What I was wondering is how I can write a Javascript function that I can pass items to inside the curly braces? I know you can write functions like this:

function someName(var1, var2, var3...) {

}

but that doesn't support the braces? I also know that you can add no arguments and do this:

function accident() {
    for( var i = 0; i < arguments.length; i++ ) {
        alert("This accident was caused by " + arguments[i]);
    }
}
accident("me","a car","alcohol","a tree that had no right to be in the path of my driving");

but I also want to pass outside variables instead of just a whole line of strings, if that makes sense?

Basically, I want a function that I can pass variables to, like so:

function myFunction(neededcodehere){
    //Some code here...
}

myFunction (var1, {"Option 1", "Option 2", "Option 3"}, anothervar);

FWIW, {"Option 1", "Option 2", "Option 3"} and var 1 are not valid JavaScript. — Felix Kling
– Felix Kling, Commented Oct 14, 2011 at 7:46
Wraith, I would just like to point out that if your passing pre-declared variables, your function will already be able to access them without any special syntax (as long as they're not nested within some other function). — Marlin
– Marlin, Commented Oct 14, 2011 at 7:59
Hey Marlin, they aren't going to be pre-declared, I wrote it wrong, its going to look something like myFunction("Title", {"Option 1" : "option1name", "Option 2" : "option2name"}, true) — Patch
– Patch, Commented Oct 14, 2011 at 8:01

Felix Kling · Accepted Answer · 2021-01-15 21:22:56Z

139

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.

edited Jan 15, 2021 at 21:22

answered Oct 14, 2011 at 7:48

Felix Kling

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5 Comments

Normajean Over a year ago

Do you know how to set a default value if, say, the foo value wasn't passed? Such that someFunc({bar: "works!"}); still generates the alerts saying "This" and "works!"

Manuel Guzman Over a year ago

@Normajean You create a defaults object with same properties and merge with the arguments object. See my answer below as the formatting in comments is poor

w3Develops Over a year ago

Here's an updated url to MDN JS Guide: developer.mozilla.org/en-US/docs/Web/JavaScript/Guide

Arash Over a year ago

Hi @Felix. what if that object has a function? it is called immediately. how can i prevent this?

Felix Kling Over a year ago

@Arash: You should post an actual question. I'm missing a lot of context here but creating an object that contains a function as a property does not automatically call said function. If it does in your case then your code is (intentionally or unintentionally) set up to do that.

Darin Dimitrov · Accepted Answer · 2011-10-14 07:44:57Z

11

function myFunction(arg) {
    alert(arg.var1 + ' ' + arg.var2 + ' ' + arg.var3);
}

myFunction ({ var1: "Option 1", var2: "Option 2", var3: "Option 3" });

answered Oct 14, 2011 at 7:44

Darin Dimitrov

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1 Comment

Ronnie Smith Over a year ago

Right. ...I was tyring to JSON.parse() my object literal. ...it was already parsed! ...doh!

Manuel Guzman · Accepted Answer · 2020-09-24 21:27:28Z

7

Answering normajeans' question about setting default value. Create a defaults object with same properties and merge with the arguments object

If using ES6:

    function yourFunction(args){
        let defaults = {opt1: true, opt2: 'something'};
        let params = {...defaults, ...args}; // right-most object overwrites 
        console.log(params.opt1);
    }

Older Browsers using Object.assign(target, source):

    function yourFunction(args){
        var defaults = {opt1: true, opt2: 'something'};
        var params = Object.assign(defaults, args) // args overwrites as it is source
        console.log(params.opt1);
    }

answered Sep 24, 2020 at 21:27

Manuel Guzman

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Comments

ofir_aghai · Accepted Answer · 2023-05-02 14:44:42Z

2

in this way:

no need to change your function signature and your function calls.
support defaults overrides.
use ES6 object destrrcturing.

function yourFunction(args) {
    let defaults = {opt1: true, opt2: 'something'};
    let params = {...defaults, ...args}; // right-most object overwrites 
    const {opt1, opt2, opt3} = params
    console.log(opt1);
}

edited May 2, 2023 at 14:44

answered May 2, 2023 at 14:38

ofir_aghai

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Comments

kqvanity · Accepted Answer · 2020-09-16 06:40:17Z

0

when you pass an object within curly braces as an argument to a function with one parameter , you're assigning this object to a variable which is the parameter in this case

answered Sep 16, 2020 at 6:40

kqvanity

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Comments

Philippe Perret · Accepted Answer · 2022-09-02 17:50:31Z

0

My cents.

function readable(args) {
    const {opt1, opt2, opt3} = args

 
    console.log(opt1 + opt2 + opt3)
    // => "My favorite things"
}


readable({
      opt1: "My f"
    , opt2: "avori"
    , opt3: "te things"
})

answered Sep 2, 2022 at 17:50

Philippe Perret

786 bronze badges

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