Javascript If statement not having correct result

I’m trying to get a button to change from one of three states to another in Javascript.
This is not working.

I’m using the following

function button1() {
    if (butt1 = "Blank") {
        butt1 = "O"
        row1[0].innerHTML = "O"
        console.log("O")
        sleep(1000)
    } else if (butt1 = "O") {
        butt1 = "X"
        row1[0].innerHTML = "X"
        console.log("X")
        sleep(1000)
    } else if (butt1 = "X") {
        butt1 = "O"
        row1[0].innerHTML = "O"
        console.log("O")
        sleep(1000)
    }
}

But I can only get the button to change from "Blank" to "O", after which point I get stuck on "O".
Would Anybody be able to give advice on how I can fix this?
Thanks for reading.

{Edit: I know it’s not very pretty or efficient but it’s all that I’ve come up with so far.}

>Solution :

Use assignment operator === in place of = in if conditions