Void function return value is used JavaScript

Question

let btn = document.createElement("button");
btn.id = "submitBV"
let firstRow = 12
let lastRow = 59
btn.addEventListener("click", autoInput(firstRow, lastRow))

function autoInput(firstRow, lastRow){
    print()
}

It tells me Void function return value is used (screenshot).

After I add a return 1, it doesn't solve as well (screenshot2).

[`.addEventListener()`](https://developer.mozilla.org/en-US/docs/Web/API/EventTarget/addEventListener) expects a callback function as its second argument. You're currently invoking `autoInput()`, thus passing its return value to `.addEventListener()`. You can pass an [anonymous function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions#the_function_expression_function_expression) which invokes `autoInput()` instead, `btn.addEventListener("click", () => autoInput(firstRow, lastRow))`. — khan, May 19 '21 at 02:46

score 9 · Accepted Answer · edited Aug 22 '22 at 12:36

Yes, because you are invoking the autoInput function which does not return something (void) valid. To handle this, to need to pass a function in order to be called when the click event is triggered by the button. In this case, you can add a simple function to do this.

btn.addEventListener("click", function() { autoInput(firstRow, lastRow); })

If you have a function which returns another function (if you are new to javascript, yes, it is possible) it may work fine, which is not your case on the autoInput function.

Void function return value is used JavaScript

1 Answers1