JQuery script runs twice in a branch

Question

I use twigfor my templates. when I load the jqueryscript in {% js_block %}, it will load twice, and I don’t know why? But when I move my script out {% js_block %}, it works correctly. what is the problem?

{% extends 'layout/base.html.twig' %}
{% block js_block %}
<script>alert('Hi')</script>
{% endblock %}

Solution: I find a problem. I was uploaded {% js_block %}to {% body_block %}:

{% extends 'layout/base.html.twig' %}
{% block body_block %}
//HTML CODES
{% block js_block %}
<script>alert('Hi')</script>
{% endblock %}
{% endblock %}

Decision:

{% extends 'layout/base.html.twig' %}
{% block body_block %}
//HTML CODES
{% endblock %}
{% block js_block %}
<script>alert('Hi')</script>
{% endblock %}

Answer 1

, script ajax .
script, 'click' , .
, , .
"ID" "class".

Answer 2

, 'click' -.