Link_to Image_tag onclick 失火（Rails + JS）

Question

I noticed this weird behavior when I do the following:

 <%= link_to(image_tag('some_image', class:"some_class", onclick:"someFunction(event)"),some_path) %>

later calling event.target; returns undefined . I investigated this and it is because the event is the image_tag instead of the link_to .

so I guess my question is: why does this happen and how do I prevent it?

I ended up splitting the link and the image and putting the onclick on the link_to (the image is obviously not clickable and there's this ugly button under it, just curious if there is a way around this.

Thanks in advance!

Answer 1

Events traverse up the dom tree, aka bubble up. target returns the element where the click happened. currentTarget returns the element where handler function is attached.

<a onclick="clickable(event)" href="#">
  <img src="/assets/sample.jpg">        <!-- if you click `img` -->
</a>

<script type="text/javascript">
  function clickable(event){
    console.log(event.target)           <!-- this will return `img` -->
    console.log(event.currentTarget)    <!-- this will return `a` -->
  }
</script>

<a onclick="clickable(event)" href="#"> <!-- if you click `a` -->
  <img src="/assets/sample.jpg">     
</a>

<script type="text/javascript">
  function clickable(event){
    console.log(event.target)           <!-- this will return `a` -->
    console.log(event.currentTarget)    <!-- this will return `a` -->
  }
</script>

If you need to get the link, make sure onclick is on the link and then call currentTarget .

Answer 2

This will add link to image and event.target will be image.

<%= link_to image_tag('some_image', class:"some_class"), some_path, onclick: "someFunction(event)" %>