JavaScript onclick事件问题

Question

Let me start off by saying my JavaScript skills are lacking, to say the least. I have been having a problem with the following function:

function setClickHandler(element) {
    element.onchange = function () {
        var id = this.options[this.selectedIndex].value;
        if(document.getElementById(id) !== null){
            clickHandler = document.getElementById(id).onclick;
        } else {
            clickHandler ="runMe('" + this.id + "','" + id + "','','null')"; }
        clickHandler.apply(this);
    }
}

Basically what it does is if a element exists with the "id" then use that elements onclick function and if it doesn't exist then create the one within the function. Then apply this onclick function to the element.

Everything works except if the "id" does not exist and it goes into the else statement where the clickHandler has to be created. I cannot figure out why this won't work. I did notice when I logged it if clickHandler was taken from another existing id then clickHandler outputted something like (onclick).event where if it went into the else statement it outputted runMe('24','54','','null').

I hope I am explaining this well enough. Any help would be greatly appreciated, thanks!

Answer 1

you're creating a string in the else case, which you can't call as a function. try this

if (document.getElementById(id) !== null) {
    clickHandler = document.getElementById(id).onclick;
    clickHandler.apply(this);
}
else {
    // clickHandler = "runMe('" + this.id + "','" + id + "','','null')";
    var runMeArgs = [this.id, id, '', 'null'];
    runMe.apply(this, runMeArgs);
}

Answer 2

In one case you're setting clickHandler to a function, in the other case you're setting it to a string?

if (...) {
   ...
} else {
   var me = this;
   clickHandler = function() {
      runMe(me.id, id, '', null);
   }
}
...

Possibly.