I think you are over complicated things a bit. Do you really need to trigger a click on the input from your button ?
I suggest you just apply a proper style to your input and the ngFileSelect directive will do the rest and call your onFileSelect function whenever a file is submitted :
input.file {
cursor: pointer;
direction: ltr;
font-size: 23px;
margin: 0;
opacity: 0;
position: absolute;
right: 0;
top: 0;
transform: translate(-300px, 0px) scale(4);
}