JavaScript adding an onclick event to a element

Question

My aim is to add an onClick event to an element when the screen is below 700px wide and to remove the clickable area if its above 700px. Am I going about this in a good way? How would I add onClick="myFunction()" to a div in HTML?

myFunction();
window.addEventListener("resize", function(event) {
    myFunction();
});
function myFunction() {
    var i = document.all?document.body.clientWidth:window.innerWidth; 
    if(i > 701) {
        // Adds onClick
    }
    if(i < 701) {
        // Removes onClick
    }
}

Answer 1

var element = document.getElementById("id");
element.addEventListener("click", function(){
});

fiddle

Answer 2

As already said by Timovski to assign onClick to div , give some id to the div and declare var.

var element = document.getElementById('divID');

than simply add eventListener to the declared var.