How to store local variables in jQuery click funct

问题:

I'm trying to figure out how to store external variable values in the functions created during jQuery's click() event. Here's a sample of the code I'm working with now.

for(var i=0; i<3; i++){
    $('#tmpid'+i).click(function(){
        var gid = i;
        alert(gid);
    });
}

<div id="tmpid0">1al</div>
<div id="tmpid1">asd</div>
<div id="tmpid2">qwe</div>

So what's happening is that the events are attaching properly, but the value of 'gid' is always the last incremented value of 'i'. I'm not sure how to setup the private variable in this situation.

回答1:

You can create a closure and assign i to a local variable of the closure. The gid variable will then be assigned the value of i at the point that the closure was created rather than when the function is run.

for(var i=0; i<3; i++){
    (function() {
        var gid = i;
        $('#tmpid'+i).click(function(){
            alert(gid);
        });
    })();
}

回答2:

for(var i=0; i<3; i++){
    $('#tmpid'+i).click((function(gid){
        return function(){
             alert(gid);
        }
    })(i));
}

there are many ways to do it, this one works and looks easy.

edit

another way:

for(var i=0; i<3; i++){
    $('#tmpid'+i).click([i],function(e){
        alert(e.data[0]);
    });

回答3:

You've created a closure, where the variable "i" is shared between multiple click handlers.

Since Javascript doesn't have block scope, you'll need to pass "i" to a new function so it is copied-by-value to a new instance:

function bindStuff(i) {
    $('#tmpid'+i).click(function(e){
                    var gid = i;
                    alert(gid);
            });
}

for(var i=0; i<3; i++){ bindStuff(i); }

Here's another similar question: JavaScript closure inside loops – simple practical example

回答4:

Alternatively, the first argument of click (or bind) for jQuery is an object that gets attached to the event as data.

for(var i=0; i<3; i++){
    $('#tmpid'+i).click({gid : i}, function(e) {
        alert(e.data.gid);
    });
}

I find this a little more readable than the closure solution, but it comes down to taste.

回答5:

I read back up on jQuery's native data() method. I implemented this and it works as well. Its hiding some of the actual functionality of how the closures are being handled, but its simple and pretty clean to implement.