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How to click on the photo response functions in the Shapespark

I write javascript code as follows to realize walk straight function, but I don’t know how to do next.

//zoom-in is a picture
document.getElementById("zoom-in").onclick =
//click picture to response key"w"(walk straight) function
    function wkey(){
    $(document).keydown(function (w){
        //don't know how to coding....

Is there have any ways to only click or hold the customized picture to realize walk straight function, not controled by shortcuts, mouse wheel on PC?