Event listener on data change in array node js

Question

I have an array with size of 3. I need to call a function dynamically when the array value is changed. Any idea?

var arr = ["","",""];

arr[0] = 'first value is chagned';
arr[1] = 'second value is chagned';


function arrFunction(){
    console.log('Array value changed')
}

Expected output

Array value changed

.

I know we can achive this by calling function directly like below. For your reference, I gave these inputs. I can not directly call function like below

var arr = ["","",""];

arr[0] = 'first value is chagned';
arrFunction()
arr[1] = 'second value is chagned';
arrFunction()

function arrFunction(){
    console.log('Array value changed')
}

why not use a function to change the value and call print together? — Farhan Qasim, Jan 29 '18 at 12:01
For your reference, I gave these inputs. I can not directly call this function — Vigneswaran A, Jan 29 '18 at 12:03
I think you might be after using a proxy -> https://stackoverflow.com/questions/35610242/detecting-changes-in-a-javascript-array-using-the-proxy-object — Keith, Jan 29 '18 at 12:11

score 3 · Accepted Answer · answered Jan 29 '18 at 12:21

if your target support Proxies this is easy to do:

let observe = (obj, fn) => new Proxy(obj, {
    set(obj, key, val) {
        obj[key] = val;
        fn(obj)
    }
});

arr = observe(['', '', ''], arr => {
    console.log('arr changed! ', arr)
});

arr[0] = 'first value is chagned';
arr[1] = 'second value is chagned';

Event listener on data change in array node js

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