How to access the function property of a javascript object using variable

Question

Hi consider below code

 let test={
    a:function(){
      console.log('Hi')
    }
  }

Is there a way to invoke property 'a' using a variable ?

This works ,

 let test={
    a:function(tmp){
      console.log(tmp)
    }
  }
let functn='a';  
test[functn]("hello");

but is there anyway to invoke the same like below code :

 let test={
    a:function(){
      console.log('Hi')
    }
  }
let functn='a("hello")';  
test.function;

The actual use case:

This is protractor system test related question,

I have a parent object with css locator [id=1] and the child elements has the locators [id=1]>div , [id=1]>span etc.

so currently parent element is stored as

let parent = element(by.css('[id=1']) ,

child as

let child1= element(by.css('[div]')

So to find all child elements of the parent element the function is :

element(by.css('[id=1']).element(by.css('[div]')

so instead of writing the locator again, i want to achieve:

parent.child1

b = test.a; b()? Though this won't work, if the method contains this keyword. — Teemu
– Teemu, Commented Jan 7, 2020 at 15:47
You mean like const fnct = {name: "a", args: ["hello"]}? With that, you can do test[fnct.name].apply(null, fnct.args). But no, a("hello"); will never work. — Bergi
– Bergi, Commented Jan 7, 2020 at 15:49
So you want to executed a piece of JavaScript that is inside a string? Why? This sounds like an XY problem. What are you trying to solve by doing it like that? — Ivar
– Ivar, Commented Jan 7, 2020 at 15:53
hi this protractor test related , i have a parent object with css locator [id=1] and the child elements are [id=1]>div , [id=1]>span etc. so currently parent element is stored as let parent = element(by.css('[id=1']) , child as let child1= element(by.css('[div]') — tsst
– tsst, Commented Jan 7, 2020 at 15:56

Quentin · Accepted Answer · 2020-01-07 15:46:01Z

1

This works ,

Yes, it does. Do that.

but is there anyway to invoke the same like below code :

No.

let functn=a("hello"); calls the function in the variable a and assigns its return value to functn.

Assuming that doesn't fail (because a isn't declared), then test.function looks at the value of the property named function (which has nothing to do with the variable function you just declared) on the object stored in test and does nothing with it.

answered Jan 7, 2020 at 15:46

Quentin

949k136 gold badges1.3k silver badges1.4k bronze badges

Sign up to request clarification or add additional context in comments.

Comments

tsst · Accepted Answer · 2020-01-07 16:18:43Z

1

Was able to make it work, i am converting everything to string and calling it using eval function:

     let test={
        a:function(tmp){
          document.write(tmp)
        }
      }
    let functn='a("hello")';
    eval(Object.keys({test})[0]+'.'+functn)

edited Jan 7, 2020 at 16:18

answered Jan 7, 2020 at 16:11

tsst

471 silver badge7 bronze badges

Comments

Addis · Accepted Answer · 2020-01-07 15:55:08Z

0

If in case you are looking for a currying solution:

 let test={
    a:function(str){
      return () => console.log(str)
    }
  }
let functn=test.a("hello");  
functn();

answered Jan 7, 2020 at 15:55

Addis

2,5402 gold badges16 silver badges21 bronze badges

Comments

user2628521 · Accepted Answer · 2020-01-07 15:56:28Z

0

At first you are passing a string which is not neccessary if you dont accept any parameters. What you can do is using getters.

Documentation: https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Functions/get

let test={
   get a (){
     console.log('Hi')
   }
}

So every time you are trying to access a it will be executed and so will print you 'Hi' in your console.

test.a;

answered Jan 7, 2020 at 15:56

user2628521

Comments

Elias Dos Reis · Accepted Answer · 2020-01-07 16:18:06Z

0

There is and simpler form of the code

// Using Function Arrow
let test = (message => 'Hello World!')()

console.log(test)

// Using factory function

let data = function() {
    return {
        nome:'Jack'
    }
}

console.log(data())
console.log(Object.values(data()))

edited Jan 7, 2020 at 16:18

answered Jan 7, 2020 at 15:50

Elias Dos Reis

11 bronze badge

Comments

Nina Scholz · Accepted Answer · 2020-01-07 16:33:00Z

0

You could change your approach to one without using eval by taking an array of key and parameter and a function which take the key and parameter and calls the function of the object.

let call = ([key, parameter]) => test[key](parameter),
    test = {
        a: function(tmp) { console.log(tmp); }
    },
    parameters = ['a', 'hello'];

call(parameters);

answered Jan 7, 2020 at 16:33

Nina Scholz

388k26 gold badges367 silver badges417 bronze badges

Collectives™ on Stack Overflow

How to access the function property of a javascript object using variable

6 Answers 6

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

6 Answers 6

Comments

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related