Javascript添加侦听器错误：TypeError：trigger.addEventListener不是函数

Question

I'm adding listeners to one link or multiple links, using the following code:

 function getData() {
            var context = {};
            context['triggers'] = triggers();
            context['msg'] = msg;
            return context
        }

function triggers() {
            var arr = [];
            document.querySelectorAll('.trigger').forEach(function (trigger, index) {
                arr[index] = {};
                arr[index]['trigger'] = trigger;
            });
            return arr;
        }



function addListeners(data) {
            data.triggers.forEach(function (trigger) {
                trigger.addEventListener('click', change)
            });
        }

data = geData()

Trigger is an anchor:

I get the following error:

TypeError: trigger.addEventListener is not a function

Answer 1

The object in triggers isn't the anchor, it's an object that contains the anchor as a property called trigger . So:

function addListeners(data) {
    data.triggers.forEach(function (entry) {            // *** `entry` instead of `trigger`
        entry.trigger.addEventListener('click', change)
// -----^^^^^^
    });
}

We know this because of this code:

function triggers() {
    var arr = [];
    document.querySelectorAll('.trigger').forEach(function (trigger, index) {
        arr[index] = {};
        arr[index]['trigger'] = trigger;
    });
    return arr;
}

That's clearly creating an object, then setting the element as a trigger property on it.

---

Side note: You can use property initializers and property literal syntax in several places where you're using strings, and FWIW you can apply map to a NodeList :

function getData() {
    return {
        triggers: triggers(),
        msg: msg
    };
}

function triggers() {
    return Array.prototype.map.call(
        document.querySelectorAll('.trigger'),
        function(anchor) {
            return {trigger: anchor};
        }
    );
}

function addListeners(data) {
    data.triggers.forEach(function (entry) {
        entry.trigger.addEventListener('click', change)
    });
}

data = geData();